the act of vibrating, or the state of being vibrated, or in vibratory motion; quick motion to and fro; oscillation, as of a pendulum or musical string.-a limited reciprocating motion of a particle of an elastic body or medium in alternately opposite directions from its position of equilibrium, when that equilibrium has been disturbed, as when a stretched cord or other body produces musical notes, or particles of air transmit sounds to the ear. the path of the particle may be in a straight line, in a circular arc, or in any curve whatever.