Source : Webster's Revised Unabridged Dictionary (1913)

Reciprocate \Re*cip"ro*cate\, v. t.
   To give and return mutually; to make return for; to give in
   return; to unterchange; to alternate; as, to reciprocate
   favors. --Cowper.

Reciprocate \Re*cip"ro*cate\, v. i. [imp. & p. p.
   {Reciprocated}; p. pr. & vb. n. {Reciprocating}.] [L.
   reciprocatus, p. p. of reciprocare. See {Reciprocal}.]
   To move forward and backward alternately; to recur in
   vicissitude; to act interchangeably; to alternate.

         One brawny smith the puffing bellows plies, And draws
         and blows reciprocating air.             --Dryden.

   {Reciprocating engine}, a steam, air, or gas engine, etc., in
      which the piston moves back and forth; -- in distinction
      from a rotary engine, in which the piston travels
      continuously in one direction in a circular path.

   {Reciprocating motion} (Mech.), motion alternately backward
      and forward, or up and down, as of a piston rod.

Source : WordNet®

reciprocate
     v 1: act, feel, or give mutually or in return; "We always invite
          the neighbors and they never reciprocate!"
     2: alternate the direction of motion of; "the engine
        reciprocates the propeller"