The Collaborative International Dictionary of English v.0.48:

Swirl \Swirl\, v. t. & i. [imp. & p. p. Swirled; p. pr. & vb.
   n. Swirling.] [Akin to Norw. svirla to whirl, freq. of
   sverra to whirl, Dan. svirre, G. schwirren to whiz, to buzz.
   [root]177. See Swarm, n.]
   To whirl, or cause to whirl, as in an eddy. "The river
   swirled along." --C. Kingsley.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Swirl \Swirl\, n.
   A whirling motion; an eddy, as of water; a whirl. "The silent
   swirl of bats." --Mrs. Browning.
   [1913 Webster]

WordNet (r) 3.0 (2006):

swirl
    n 1: the shape of something rotating rapidly [syn: whirl,
         swirl, vortex, convolution]
    v 1: turn in a twisting or spinning motion; "The leaves swirled
         in the autumn wind" [syn: twirl, swirl, twiddle,
         whirl]
    2: flow in a circular current, of liquids [syn: eddy, purl,
       whirlpool, swirl, whirl]