The Collaborative International Dictionary of English v.0.48:

Maelstrom \Mael"strom\, n. [Norw., a whirlpool.]
   1. A celebrated whirlpool on the coast of Norway. Hence: any
      large or powerful whirlpool.

   Syn: whirlpool, vortex.
        [1913 Webster]

   2. Also (Fig.) An uncontrollable agitated or confusedly
      disordered state or situation; as, a maelstrom of vice.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

maelstrom
    n 1: a powerful circular current of water (usually the result of
         conflicting tides) [syn: whirlpool, vortex,
         maelstrom]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "maelstrom":
   Charybdis, Maelstrom, ado, agitation, back stream, backflow,
   backwash, backwater, bluster, bobbery, boil, boiling, bother,
   botheration, brouhaha, burst, bustle, churn, commotion, confusion,
   conturbation, countercurrent, counterflow, counterflux,
   discomposure, disorder, disquiet, disquietude, disturbance,
   dizzy round, ebullition, eddy, embroilment, excitement, feery-fary,
   ferment, fermentation, fever, feverishness, fidgetiness, fidgets,
   fit, flap, flurry, fluster, flutter, flutteration, flutteriness,
   foment, fume, fury, fuss, fussiness, gulf, gurge, gyre, hubbub,
   hullabaloo, hurly-burly, inquietude, jitters, jumpiness, malaise,
   moil, nerviness, nervosity, nervousness, perturbation, pirouette,
   pother, rat race, reel, refluence, reflux, regurgitation,
   restlessness, roil, round, rout, row, scramble, seethe, seething,
   spasm, spin, spurt, stew, stir, storm, surge, sweat, swirl, to-do,
   trepidation, trepidity, tumult, tumultuation, turbidity,
   turbulence, turmoil, turn, twirl, twitter, unease, unquiet, unrest,
   upset, vortex, wheel, whirl, whirlpool, whirlwind