reciprocate

reciprocate is a Verb

Definition:

[1] 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.