The Collaborative International Dictionary of English v.0.48:

Pivot \Piv"ot\, n. [F.; prob. akin to It. piva pipe, F. pipe.
   See Pipe.]
   1. A fixed pin or short axis, on the end of which a wheel or
      other body turns.
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   2. The end of a shaft or arbor which rests and turns in a
      support; as, the pivot of an arbor in a watch.
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   3. Hence, figuratively: A turning point or condition; that on
      which important results depend; as, the pivot of an
      enterprise.
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   4. (Mil.) The officer or soldier who simply turns in his
      place whike the company or line moves around him in
      wheeling; -- called also pivot man.
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   Pivot bridge, a form of drawbridge in which one span,
      called the pivot span, turns about a central vertical
      axis.

   Pivot gun, a gun mounted on a pivot or revolving carriage,
      so as to turn in any direction.

   Pivot tooth (Dentistry), an artificial crown attached to
      the root of a natural tooth by a pin or peg.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pivot man
    n 1: the person in a rank around whom the others wheel and
         maneuver [syn: pivot, pivot man]