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]

Moby Thesaurus II by Grady Ward, 1.0:

184 Moby Thesaurus words for "swirl":
   Charybdis, Maelstrom, ado, agitate, agitation, back stream,
   backflow, backwash, backwater, beat, beat up, bluster, bobbery,
   boil, boiling, bother, botheration, brouhaha, burst, bustle,
   centrifugate, centrifuge, churn, churn up, circulate, cirrus, coil,
   commotion, contort, conturbation, convulse, corkscrew,
   countercurrent, counterflow, counterflux, crinkle, curl, curlicue,
   curve, disarrange, discompose, discomposure, disorder, disquiet,
   disquietude, disturb, disturbance, dizzy round, ebullience,
   ebullition, eddy, effervescence, embroilment, evolute, excite,
   excitement, feery-fary, ferment, fermentation, fever, feverishness,
   fidgetiness, fidgets, fit, flap, flurry, fluster, flutter,
   flutteration, flutteriness, foment, fret, fume, furl, fuss,
   fussiness, gulf, gurge, gush, gyrate, gyre, helix, hubbub,
   hullabaloo, hurly-burly, hurry, hurry-scurry, inquietude, intort,
   involute, jitters, jumpiness, kink, maelstrom, malaise, meander,
   moil, nerviness, nervosity, nervousness, paddle, pell-mell,
   perturb, perturbate, perturbation, pirouette, pother, purl,
   rat race, reel, refluence, reflux, regurgitation, restlessness,
   rile, ringlet, ripple, roil, roll, roughen, round, rout, row,
   ruffle, rumple, scallop, scramble, screw, scroll, seethe, seething,
   serpentine, shake, shake up, slink, snake, spasm, spin, spiral,
   spurt, stew, stir, stir up, surge, sweat, swirling, tendril, to-do,
   trepidation, trepidity, trouble, tumult, tumultuation, turbidity,
   turbulence, turmoil, turn, twine, twirl, twist, twist and turn,
   twitter, unease, unquiet, unrest, uproar, upset, volute, volution,
   vortex, wheel, whip, whip up, whirl, whirligig, whirlpool,
   whirlwind, whisk, whorl, wind, work up, worm, wring, yeastiness