Arm n.
 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.