The Collaborative International Dictionary of English v.0.48:

Fluffy \Fluff"y\, a. [Compar. Fluffier; superl. Fluffiest.]
   Pertaining to, or resembling, fluff or nap; soft and downy.
   "The carpets were fluffy." --Thackeray.
   [1913 Webster]

         The present Barnacle . . . had a youthful aspect, and
         the fluffiest little whisker, perhaps, that ever was
         seen.                                    --Dickens.
   -- Fluff"i*ness, n.
   [1913 Webster] Flugel

WordNet (r) 3.0 (2006):

fluffy
    adj 1: like down or as soft as down [syn: downy, downlike,
           flossy, fluffy]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "fluffy":
   airy, attenuate, attenuated, birdbrained, birdwitted, bubbly,
   dainty, delicate, downy, ethereal, featherbrained, feathery, filmy,
   fine, fine-drawn, fine-grained, finespun, fleecy, flighty, flossy,
   foamy, frivolous, frothy, furry, fuzzy, gauzy, gossamer, gossamery,
   hirsute, imponderous, insubstantial, lanate, leger, light,
   light as air, lighter than vanity, lightweight, mousse, nappy,
   peachy, pinnate, pubescent, puffy, refined, satin, satiny, shallow,
   shallow-headed, shallow-minded, shallow-pated, shallow-witted,
   silky, smooth, soft, souffle, superficial, thin, thin-spun,
   trivial, unheavy, unimportant, unprofound, velutinous, velvety,
   volatile, weightless, whipped up, wiredrawn, wispy, woolly,
   yeasty