1. (n.) 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.

2. (n.) 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.

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