1. [n]  a base hit on which the batter stops safely at second base; "he hit a double to deep centerfield"
2. [n]  raising the stakes in a card game by a factor of 2; "I decided his double was a bluff"
3. [n]  a quantity that is twice as great as another; "36 is the double of 18"
4. [n]  someone who closely resembles a famous person (especially an actor); "he could be Gingrich's double"; "she's the very image of her mother"
5. [n]  a stand-in for movie stars to perform dangerous stunts; "his first job in Hollywood was as a double for Clark Gable"
6. [adv]  to double the degree; "she was doubly rewarded"; "his eyes were double bright"
7. [adv]  two together; "some people sleep better double"
8. [adv]  downward and forward; "he was bent double with pain"
9. [adj]  having two meanings with intent to deceive; "a sly double meaning"; "spoke with forked tongue"
10. [adj]  large enough for two; "a double bed"; "a double room"
11. [adj]  (genetics) used of homologous chromosomes associated in pairs in synapsis
12. [adj]  twice as great or many; "ate a double portion"; "the dose is doubled"; "a twofold increase"
13. [adj]  consisting of or involving two parts or components usually in pairs; "an egg with a double yolk"; "a double (binary) star"; "double doors"; "dual controls for pilot and copilot"; "duple (or double) time consists of two (or a multiple of two) beats to a measure"
14. [adj]  having more than one decidedly dissimilar aspects or qualities; "a double (or dual) role for an actor"; "the office of a clergyman is twofold; public preaching and private influence"- R.W.Emerson; "every episode has its double and treble meaning"-Frederick Harrison
15. [adj]  (botany; of flowers) having more than the usual number of petals in crowded or overlapping arrangements; "double chrysanthemums have many rows of petals and are usually spherical or hemispherical"
16. [v]  increase twofold; "The population doubled within 50 years"
17. [v]  hit a two-base hit, in baseball
18. [v]  do double duty; serve two purposes or have two functions; "She doubles as his wife and secretary"
19. [v]  make or do or perform again; "He could never replicate his brilliant performance of the magic trick"
20. [v]  bend over or curl up, usually with laughter or pain; "He doubled and vomited violently"

Double
Double

more details ...

1. \Dou"ble\, a. [OE. doble, duble, double, OF. doble,
   duble, double, F. double, fr. L. duplus, fr. the root of duo
   two, and perh. that of plenus full; akin to Gr. ? double. See
   {Two}, and {Full}, and cf. {Diploma}, {Duple}.]
   1. Twofold; multiplied by two; increased by its equivalent;
      made twice as large or as much, etc.
            Let a double portion of thy spirit be upon me. -- 2
                                                  Kings ii. 9.
            Darkness and tempest make a double night. --Dryden.
   2. Being in pairs; presenting two of a kind, or two in a set
      together; coupled.
            [Let] The swan, on still St. Mary's lake, Float
            double, swan and shadow.              --Wordsworth.
   3. Divided into two; acting two parts, one openly and the
      other secretly; equivocal; deceitful; insincere.
            With a double heart do they speak.    -- Ps. xii. 2.
   4. (Bot.) Having the petals in a flower considerably
      increased beyond the natural number, usually as the result
      of cultivation and the expense of the stamens, or stamens
      and pistils. The white water lily and some other plants
      have their blossoms naturally double.
   Note: Double is often used as the first part of a compound
         word, generally denoting two ways, or twice the number,
         quantity, force, etc., twofold, or having two.
   {Double base}, or {Double bass} (Mus.), the largest and
      lowest-toned instrument in the violin form; the
      contrabasso or violone.
   {Double convex}. See under {Convex}.
   {Double counterpoint} (Mus.), that species of counterpoint or
      composition, in which two of the parts may be inverted, by
      setting one of them an octave higher or lower.
   {Double court} (Lawn Tennis), a court laid out for four
      players, two on each side.
   {Double dagger} (Print.), a reference mark ([dag]) next to
      the dagger ([dagger]) in order; a diesis.
   {Double drum} (Mus.), a large drum that is beaten at both
      ends.
   {Double eagle}, a gold coin of the United States having the
      value of 20 dollars.
   {Double entry}. See under {Bookkeeping}.
   {Double floor} (Arch.), a floor in which binding joists
      support flooring joists above and ceiling joists below.
      See Illust. of Double-framed floor.
   {Double flower}. See {Double}, a., 4.
   {Double-framed floor} (Arch.), a double floor having girders
      into which the binding joists are framed.
   {Double fugue} (Mus.), a fugue on two subjects.
   {Double letter}.
      (a) (Print.) Two letters on one shank; a ligature.
      (b) A mail requiring double postage.
   {Double note} (Mus.), a note of double the length of the
      semibreve; a breve. See {Breve}.
   {Double octave} (Mus.), an interval composed of two octaves,
      or fifteen notes, in diatonic progression; a fifteenth.
   {Double pica}. See under {Pica}.
   {Double play} (Baseball), a play by which two players are put
      out at the same time.
   {Double plea} (Law), a plea alleging several matters in
      answer to the declaration, where either of such matters
      alone would be a sufficient bar to the action. --Stephen.
   {Double point} (Geom.), a point of a curve at which two
      branches cross each other. Conjugate or isolated points of
      a curve are called double points, since they possess most
      of the properties of double points (see {Conjugate}). They
      are also called {acnodes}, and those points where the
      branches of the curve really cross are called {crunodes}.
      The extremity of a cusp is also a double point.
   {Double quarrel}. (Eccl. Law) See {Duplex querela}, under
      {Duplex}.
   {Double refraction}. (Opt.) See {Refraction}.
   {Double salt}. (Chem.)
      (a) A mixed salt of any polybasic acid which has been
          saturated by different bases or basic radicals, as the
          double carbonate of sodium and potassium,
          {NaKCO3.6H2O}.
      (b) A molecular combination of two distinct salts, as
          common alum, which consists of the sulphate of
          aluminium, and the sulphate of potassium or ammonium.
   {Double shuffle}, a low, noisy dance.
   {Double standard} (Polit. Econ.), a double standard of
      monetary values; i. e., a gold standard and a silver
      standard, both of which are made legal tender.
   {Double star} (Astron.), two stars so near to each other as
      to be seen separate only by means of a telescope. Such
      stars may be only optically near to each other, or may be
      physically connected so that they revolve round their
      common center of gravity, and in the latter case are
      called also binary stars.
   {Double time} (Mil.). Same as {Double-quick}.
   {Double window}, a window having two sets of glazed sashes
      with an air space between them.
   

2. \Dou"ble\, adv.
   Twice; doubly.
         I was double their age.                  --Swift.
   

3. \Dou"ble\, v. t. [imp. & p. p. {Doubled}; p. pr. & vb. n.
   {Doubling}.] [OE. doblen, dublen, doublen, F. doubler, fr. L.
   duplare, fr. duplus. See {Double}, a.]
   1. To increase by adding an equal number, quantity, length,
      value, or the like; multiply by two; to double a sum of
      money; to double a number, or length.
            Double six thousand, and then treble that. --Shak.
   2. To make of two thicknesses or folds by turning or bending
      together in the middle; to fold one part upon another part
      of; as, to double the leaf of a book, and the like; to
      clinch, as the fist; -- often followed by up; as, to
      double up a sheet of paper or cloth.
   

4. \Dou"ble\, v. i.
   1. To be increased to twice the sum, number, quantity,
      length, or value; to increase or grow to twice as much.
            'T is observed in particular nations, that within
            the space of three hundred years, notwithstanding
            all casualties, the number of men doubles. --T.
                                                  Burnet.
   2. To return upon one's track; to turn and go back over the
      same ground, or in an opposite direction.
            Doubling and turning like a hunted hare. --Dryden.
            Doubling and doubling with laborious walk.
                                                  --Wordsworth.
   3. To play tricks; to use sleights; to play false.
            What penalty and danger you accrue, If you be found
            to double.                            --J. Webster.
   4. (Print.) To set up a word or words a second time by
      mistake; to make a doublet.
   {To double upon} (Mil.), to inclose between two fires.
   

5. \Dou"ble\, n.
   1. Twice as much; twice the number, sum, quantity, length,
      value, and the like.
            If the thief be found, let him pay double. --Ex.
                                                  xxii. 7.
   2. Among compositors, a doublet (see {Doublet}, 2.); among
      pressmen, a sheet that is twice pulled, and blurred.
   3. That which is doubled over or together; a doubling; a
      plait; a fold.
            Rolled up in sevenfold double Of plagues. --Marston.
   4. A turn or circuit in running to escape pursues; hence, a
      trick; a shift; an artifice.
            These men are too well acquainted with the chase to
            be flung off by any false steps or doubles.
                                                  --Addison.
   5. Something precisely equal or counterpart to another; a
      counterpart. Hence, a wraith.
            My charming friend . . . has, I am almost sure, a
            double, who preaches his afternoon sermons for him.
                                                  --Atlantic
                                                  Monthly.
   6. A player or singer who prepares to take the part of
      another player in his absence; a substitute.
   7. Double beer; strong beer.
   8. (Eccl.) A feast in which the antiphon is doubled, hat is,
      said twice, before and after the Psalms, instead of only
      half being said, as in simple feasts. --Shipley.
   9. (Lawn Tennis) A game between two pairs of players; as, a
      first prize for doubles.
   10. (Mus.) An old term for a variation, as in Bach's Suites.
   

6. \Dou"ble\, n.
   A person or thing that is the counterpart of another; a
   duplicate; copy; (Obs.) transcript; -- now chiefly used of
   persons. Hence, a wraith.
         My charming friend . . . has, I am almost sure, a
         double, who preaches his afternoon sermons for him.
                                                  --E. E. Hale.