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.
      [1913 Webster]

   2. The end of a shaft or arbor which rests and turns in a
      support; as, the pivot of an arbor in a watch.
      [1913 Webster]

   3. Hence, figuratively: A turning point or condition; that on
      which important results depend; as, the pivot of an
      enterprise.
      [1913 Webster]

   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.
      [1913 Webster]

   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]

The Collaborative International Dictionary of English v.0.48:

Pivot \Piv"ot\, v. t. [imp. & p. p. Pivoted; p. pr. & vb. n.
   Pivoting.]
   To place on a pivot. --Clarke.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pivot
    n 1: the person in a rank around whom the others wheel and
         maneuver [syn: pivot, pivot man]
    2: axis consisting of a short shaft that supports something that
       turns [syn: pivot, pin]
    3: the act of turning on (or as if on) a pivot; "the golfer went
       to the driving range to practice his pivot"
    v 1: turn on a pivot [syn: pivot, swivel]