1. [n]  the part of an armchair or sofa that supports the elbow and forearm of a seated person
2. [n]  any projection that is thought to resemble an arm; "the arm of the record player"; "an arm of the sea"; "a branch of the sewer"
3. [n]  the part of a garment that is attached at armhole and provides a cloth covering for the arm
4. [n]  instrument used in fighting or hunting; "he was licensed to carry a weapon"
5. [n]  a human limb; technically the part of the superior limb between the shoulder and the elbow but commonly used to refer to the whole superior limb
6. [n]  an administrative division of some larger or more complex organization; "a branch of Congress"
7. [v]  prepare oneselg for a military confrontation; "The U.S. is girding for a conflict in the Middle East"
8. [v]  supply with arms; "The U.S. armed the freedom fighters in Afghanistan"

ARM is a 3 letter word that starts with A.

1. \Arm\, n. [AS. arm, earm; akin to OHG. aram, G., D., Dan., &
   Sw. arm, Icel. armr, Goth. arms, L. armus arm, shoulder, and
   prob. to Gr. ? joining, joint, shoulder, fr. the root ? to
   join, to fit together; cf. Slav. rame. ?. See {Art},
   {Article}.]
   1. The limb of the human body which extends from the shoulder
      to the hand; also, the corresponding limb of a monkey.
   2. Anything resembling an arm; as,
      (a) The fore limb of an animal, as of a bear.
      (b) A limb, or locomotive or prehensile organ, of an
          invertebrate animal.
      (c) A branch of a tree.
      (d) A slender part of an instrument or machine, projecting
          from a trunk, axis, or fulcrum; as, the arm of a
          steelyard.
      (e) (Naut) The end of a yard; also, the part of an anchor
          which ends in the fluke.
      (f) An inlet of water from the sea.
      (g) A support for the elbow, at the side of a chair, the
          end of a sofa, etc.
   3. Fig.: Power; might; strength; support; as, the secular
      arm; the arm of the law.
            To whom is the arm of the Lord revealed? --Isa. lii.
                                                  1.
   {Arm's end}, the end of the arm; a good distance off.
      --Dryden.
   {Arm's length}, the length of the arm.
   {Arm's reach}, reach of the arm; the distance the arm can
      reach.
   {To go} (or {walk}) {arm in arm}, to go with the arm or hand
      of one linked in the arm of another. ``When arm in armwe
      went along.'' --Tennyson.
   {To keep at arm's length}, to keep at a distance (literally
      or figuratively); not to allow to come into close contact
      or familiar intercourse.
   {To work at arm's length}, to work disadvantageously.
   

2. \Arm\, n. [See {Arms}.] (Mil.)
      (a) A branch of the military service; as, the cavalry arm
          was made efficient.
      (b) A weapon of offense or defense; an instrument of
          warfare; -- commonly in the pl.
   

3. \Arm\, v. t. [imp. & p. p. {Armed}; p. pr. & vb. n.
   {Arming}.] [OE. armen, F. armer, fr. L. armare, fr. arma,
   pl., arms. See {arms}.]
   1. To take by the arm; to take up in one's arms. [Obs.]
            And make him with our pikes and partisans A grave:
            come, arm him.                        --Shak.
            Arm your prize; I know you will not lose him. --Two
                                                  N. Kins.
   2. To furnish with arms or limbs. [R.]
            His shoulders broad and strong, Armed long and
            round.                                --Beau. & Fl.
   3. To furnish or equip with weapons of offense or defense;
      as, to arm soldiers; to arm the country.
            Abram . . . armed his trained servants. --Gen. xiv.
                                                  14.
   4. To cover or furnish with a plate, or with whatever will
      add strength, force, security, or efficiency; as, to arm
      the hit of a sword; to arm a hook in angling.
   5. Fig.: To furnish with means of defense; to prepare for
      resistance; to fortify, in a moral sense.
            Arm yourselves . . . with the same mind. --1 Pet.
                                                  iv. 1.
   {To arm a magnet}, to fit it with an armature.
   

4. \Arm\, v. i.
   To provide one's self with arms, weapons, or means of attack
   or resistance; to take arms. `` 'Tis time to arm.'' --Shak.
   

1. advanced risc machine.

Originally acorn RISC Machine.

2. advanced risc machines Ltd.

3. ["The Annotated C++ Reference Manual", Margaret A. Ellis and Bjarne Stroustrup, Addison-Wesley, 1990].

4. active reconfiguring message.

used to denote power (Ps. 10:15; Ezek. 30:21; Jer. 48:25). It is also used of the omnipotence of God (Ex. 15:16; Ps. 89:13; 98:1; 77:15; Isa. 53:1; John 12:38; Acts 13:17)