Source : Webster's Revised Unabridged Dictionary (1913)

Swivel \Swiv"el\, n. [AS. sw[=i]fan to move quickly, to remove;
   akin to Icel. sveifla to whirl, shake, sv[=i]fa to ramble, to
   turn. See {Swoop}, and cf. {Swift} a reel, {Swift}, a.]
   1. (Mech.) A piece, as a ring or hook, attached to another
      piece by a pin, in such a manner as to permit rotation
      about the pin as an axis.

   2. (Mil.) A small piece of ordnance, turning on a point or
      swivel; -- called also {swivel gun}. --Wilhelm.

   {Swivel bridge}, a kind of drawbridge that turns round on a
      vertical axis; a swing bridge.

   {Swivel hook}, a hook connected with the iron strap of a
      pulley block by a swivel joint, for readily taking the
      turns out of a tackle.

   {Swivel joint}, a joint, the two pieces composing which turn
      round, with respect to each other, on a longitudinal pin
      or axis, as in a chain, to prevent twisting.

Swivel \Swiv"el\, v. i.
   To swing or turn, as on a pin or pivot.

Source : WordNet®

swivel
     n : a coupling (as in a chain) that has one end that turns on a
         headed pin
     [also: {swivelling}, {swivelled}]

swivel
     v : turn on a pivot [syn: {pivot}]
     [also: {swivelling}, {swivelled}]