1. [n]  the principal activity in your life that you do to earn money; "he's not in my line of business"
2. [n]  acting in conformity; "in line with"; "he got out of line"; "toe the line"
3. [n]  a conductor for transmitting electrical or optical signals or electric power
4. [n]  something (as a cord or rope) that is long and thin and flexible; "a washing line"
5. [n]  the road consisting of railroad track and roadbed
6. [n]  a commercial organization serving as a common carrier
7. [n]  a particular kind of product or merchandise; "a nice line of shoes"
8. [n]  a pipe used to transport liquids or gases; "a pipeline runs from the wells to the seaport"
9. [n]  mechanical system in a factory whereby an article is conveyed through sites at which successive operations are performed on it
10. [n]  a telephone connection
11. [n]  a conceptual separation or demarcation; "there is a narrow line between sanity and insanity"
12. [n]  the methodical process of logical reasoning; "I can't follow your line of reasoning"
13. [n]  (often plural) a means of communication or access; "it must go through official channels"; "lines of communication were set up between the two firms"
14. [n]  a short personal letter; "drop me a line when you get there"
15. [n]  a mark that is long relative to its width; "He drew a line on the chart"; "The substance produced characteristic lines on the spectroscope"
16. [n]  text consisting of a row of words written across a page or column or computer screen; "the letter consisted of three short lines"
17. [n]  a succession of notes forming a distinctive sequence; "she was humming an air from Beethoven"
18. [n]  the descendants of one individual; "his entire lineage has been warriors"
19. [n]  a connected series of events or actions or developments; "the government took a firm course"; "historians can only point out those lines for which evidence is available"
20. [n]  a formation of people or things one behind another; "the line stretched clear around the corner"; "you must wait in a long line at the checkout counter"
21. [n]  a formation of people or things one beside another; "the line of soldiers advanced with their bayonets fixed"; "they were arrayed in line of battle"; "the cast stood in line for the curtain call"
22. [n]  a spatial location defined by a real or imaginary unidimensional extent
23. [n]  in games or sports; a mark indicating positions or bounds of the playing area
24. [n]  a fortified position (especially one marking the most forward position of troops); "they attacked the enemy's line"
25. [n]  a single frequency (or very narrow band) of radiation in a spectrum
26. [n]  the maximum credit that a customer is allowed
27. [n]  space for one line of print (one column wide and 1/14 inch deep) used to measure advertising
28. [n]  a length (straight or curved) without breadth or thickness; the trace of a moving point
29. [n]  a slight depression in the smoothness of a surface; "his face has many lines"; "ironing gets rid of most wrinkles"
30. [v]  reinforce with fabric; of books
31. [v]  fill plentifully; "line one's pockets"
32. [v]  mark with lines, draw lines on; "The paper was lined"
33. [v]  cover the interior of, as of garments; "line the gloves"
34. [v]  mark with lines; "sorrow had lined his face"
35. [v]  make a mark or lines on a surface; "draw a line"; "trace the outline of a figure in the sand"
36. [v]  be in line with; form a line along; of trees along a river, etc.

1. \Line\ (l[imac]n), n. [OE. lin. See {Linen}.]
   1. Flax; linen. [Obs.] ``Garments made of line.'' --Spenser.
   2. The longer and finer fiber of flax.
   

2. \Line\, v. t. [imp. & p. p. {Lined} (l[imac]nd); p. pr. &
   vb. n. {Lining}.] [See {Line} flax.]
   1. To cover the inner surface of; as, to line a cloak with
      silk or fur; to line a box with paper or tin.
            The inside lined with rich carnation silk. --W.
                                                  Browne.
   2. To put something in the inside of; to fill; to supply, as
      a purse with money.
            The charge amounteth very high for any one man's
            purse, except lined beyond ordinary, to reach unto.
                                                  --Carew.
            Till coffee has her stomach lined.    --Swift.
   3. To place persons or things along the side of for security
      or defense; to strengthen by adding anything; to fortify;
      as, to line works with soldiers.
            Line and new repair our towns of war With men of
            courage and with means defendant.     --Shak.
   4. To impregnate; -- applied to brute animals. --Creech.
   {Lined gold}, gold foil having a lining of another metal.
   

3. \Line\, n. [OE. line, AS. l[=i]ne cable, hawser, prob. from
   L. linea a linen thread, string, line, fr. linum flax,
   thread, linen, cable; but the English word was influenced by
   F. ligne line, from the same L. word linea. See {Linen}.]
   1. A linen thread or string; a slender, strong cord; also, a
      cord of any thickness; a rope; a hawser; as, a fishing
      line; a line for snaring birds; a clothesline; a towline.
            Who so layeth lines for to latch fowls. --Piers
                                                  Plowman.
   2. A more or less threadlike mark of pen, pencil, or graver;
      any long mark; as, a chalk line.
   3. The course followed by anything in motion; hence, a road
      or route; as, the arrow descended in a curved line; the
      place is remote from lines of travel.
   4. Direction; as, the line of sight or vision.
   5. A row of letters, words, etc., written or printed; esp., a
      row of words extending across a page or column.
   6. A short letter; a note; as, a line from a friend.
   7. (Poet.) A verse, or the words which form a certain number
      of feet, according to the measure.
            In the preceding line Ulysses speaks of Nausicaa.
                                                  --Broome.
   8. Course of conduct, thought, occupation, or policy; method
      of argument; department of industry, trade, or
      intellectual activity.
            He is uncommonly powerful in his own line, but it is
            not the line of a first-rate man.     --Coleridge.
   9. (Math.) That which has length, but not breadth or
      thickness.
   10. The exterior limit of a figure, plat, or territory;
       boundary; contour; outline.
             Eden stretched her line From Auran eastward to the
             royal towers Of great Seleucia.      --Milton.
   11. A threadlike crease marking the face or the hand; hence,
       characteristic mark.
             Though on his brow were graven lines austere.
                                                  --Byron.
             He tipples palmistry, and dines On all her
             fortune-telling lines.               --Cleveland.
   12. Lineament; feature; figure. ``The lines of my boy's
       face.'' --Shak.
   13. A straight row; a continued series or rank; as, a line of
       houses, or of soldiers; a line of barriers.
             Unite thy forces and attack their lines. --Dryden.
   14. A series or succession of ancestors or descendants of a
       given person; a family or race; as, the ascending or
       descending line; the line of descent; the male line; a
       line of kings.
             Of his lineage am I, and his offspring By very
             line, as of the stock real.          --Chaucer.
   15. A connected series of public conveyances, and hence, an
       established arrangement for forwarding merchandise, etc.;
       as, a line of stages; an express line.
   16. (Geog.)
       (a) A circle of latitude or of longitude, as represented
           on a map.
       (b) The equator; -- usually called {the line}, or
           {equinoctial line}; as, to cross the line.
   17. A long tape, or a narrow ribbon of steel, etc., marked
       with subdivisions, as feet and inches, for measuring; a
       tapeline.
   18. (Script.)
       (a) A measuring line or cord.
                 He marketh it out with a line.   --Is. xliv.
                                                  13.
       (b) That which was measured by a line, as a field or any
           piece of land set apart; hence, allotted place of
           abode.
                 The lines are fallen unto me in pleasant
                 places; yea, I have a goodly heritage. --Ps.
                                                  xvi. 6.
       (c) Instruction; doctrine.
                 Their line is gone out through all the earth.
                                                  --Ps. xix. 4.
   19. (Mach.) The proper relative position or adjustment of
       parts, not as to design or proportion, but with reference
       to smooth working; as, the engine is in line or out of
       line.
   20. The track and roadbed of a railway; railroad.
   21. (Mil.)
       (a) A row of men who are abreast of one another, whether
           side by side or some distance apart; -- opposed to
           {column}.
       (b) The regular infantry of an army, as distinguished
           from militia, guards, volunteer corps, cavalry,
           artillery, etc.
   22. (Fort.)
       (a) A trench or rampart.
       (b) pl. Dispositions made to cover extended positions,
           and presenting a front in but one direction to an
           enemy.
   23. pl. (Shipbuilding) Form of a vessel as shown by the
       outlines of vertical, horizontal, and oblique sections.
   24. (Mus.) One of the straight horizontal and parallel
       prolonged strokes on and between which the notes are
       placed.
   25. (Stock Exchange) A number of shares taken by a jobber.
   26. (Trade) A series of various qualities and values of the
       same general class of articles; as, a full line of
       hosiery; a line of merinos, etc. --McElrath.
   27. The wire connecting one telegraphic station with another,
       or the whole of a system of telegraph wires under one
       management and name.
   28. pl. The reins with which a horse is guided by his driver.
       [U. S.]
   29. A measure of length; one twelfth of an inch.
   {Hard lines}, hard lot. --C. Kingsley. [See Def. 18.]
   {Line breeding} (Stockbreeding), breeding by a certain family
      line of descent, especially in the selection of the dam or
      mother.
   {Line conch} (Zo["o]l.), a spiral marine shell ({Fasciolaria
      distans}), of Florida and the West Indies. It is marked by
      narrow, dark, revolving lines.
   {Line engraving}.
       (a) Engraving in which the effects are produced by lines
           of different width and closeness, cut with the burin
           upon copper or similar material; also, a plate so
           engraved.
       (b) A picture produced by printing from such an
           engraving.
   {Line of battle}.
       (a) (Mil. Tactics) The position of troops drawn up in
           their usual order without any determined maneuver.
       (b) (Naval) The line or arrangement formed by vessels of
           war in an engagement.
   {Line of battle ship}. See {Ship of the line}, below.
   {Line of beauty} (Fine Arts),an abstract line supposed to be
      beautiful in itself and absolutely; -- differently
      represented by different authors, often as a kind of
      elongated S (like the one drawn by Hogarth).
   {Line of centers}. (Mach.)
       (a) A line joining two centers, or fulcra, as of wheels
           or levers.
       (b) A line which determines a dead center. See {Dead
           center}, under {Dead}.
   {Line of dip} (Geol.), a line in the plane of a stratum, or
      part of a stratum, perpendicular to its intersection with
      a horizontal plane; the line of greatest inclination of a
      stratum to the horizon.
   {Line of fire} (Mil.), the direction of fire.
   {Line of force} (Physics), any line in a space in which
      forces are acting, so drawn that at every point of the
      line its tangent is the direction of the resultant of all
      the forces. It cuts at right angles every equipotential
      surface which it meets. Specifically (Magnetism), a line
      in proximity to a magnet so drawn that any point in it is
      tangential with the direction of a short compass needle
      held at that point. --Faraday.
   {Line of life} (Palmistry), a line on the inside of the hand,
      curving about the base of the thumb, supposed to indicate,
      by its form or position, the length of a person's life.
   {Line of lines}. See {Gunter's line}.
   {Line of march}. (Mil.)
       (a) Arrangement of troops for marching.
       (b) Course or direction taken by an army or body of
           troops in marching.
   {Line of operations}, that portion of a theater of war which
      an army passes over in attaining its object. --H. W.
      Halleck.
   {Line of sight} (Firearms), the line which passes through the
      front and rear sight, at any elevation, when they are
      sighted at an object.
   {Line tub} (Naut.), a tub in which the line carried by a
      whaleboat is coiled.
   {Mason and Dixon's line}
   

4. \Line\ (l[imac]n), v. t.
   1. To mark with a line or lines; to cover with lines; as, to
      line a copy book.
            He had a healthy color in his cheeks, and his face,
            though lined, bore few traces of anxiety. --Dickens.
   2. To represent by lines; to delineate; to portray. [R.]
      ``Pictures fairest lined.'' --Shak.
   3. To read or repeat line by line; as, to line out a hymn.
            This custom of reading or lining, or, as it was
            frequently called, ``deaconing'' the hymn or psalm
            in the churches, was brought about partly from
            necessity.                            --N. D. Gould.
   4. To form into a line; to align; as, to line troops.
   {To line bees}, to track wild bees to their nest by following
      their line of flight.
   {To line up} (Mach.), to put in alignment; to put in correct
      adjustment for smooth running. See 3d {Line}, 19.
   

1. An electrical conductor. For distances larger than a breadbox, a single line may consist of two electrical conductors in twisted, parallel, or concentric arrangement used to transport one logical signal.

By extension, a (usually physical) medium such as an optical fibre which carries a signal.