The Collaborative International Dictionary of English v.0.48:
Vibration \Vi*bra"tion\, n. [L. vibratio: cf. F. vibration.]
1. 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.
As a harper lays his open palm
Upon his harp, to deaden its vibrations.
2. (Physics) 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
Note: Vibration and oscillation are both used, in mechanics,
of the swinging, or rising and falling, motion of a
suspended or balanced body; the latter term more
appropriately, as signifying such motion produced by
gravity, and of any degree of slowness, while the
former applies especially to the quick, short motion to
and fro which results from elasticity, or the action of
molecular forces among the particles of a body when
disturbed from their position of rest, as in a spring.
Amplitude of vibration, the maximum displacement of a
vibrating particle or body from its position of rest.
Phase of vibration, any part of the path described by a
particle or body in making a complete vibration, in
distinction from other parts, as while moving from one
extreme to the other, or on one side of the line of rest,
in distinction from the opposite. Two particles are said
to be in the same phase when they are moving in the same
direction and with the same velocity, or in corresponding
parts of their paths.