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.
      [1913 Webster]

            As a harper lays his open palm
            Upon his harp, to deaden its vibrations.
                                                  --Longfellow.
      [1913 Webster]

   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
      whatever.
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   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.
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   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.
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