The Collaborative International Dictionary of English v.0.48:

Fluff \Fluff\, n. [Cf. 2d Flue. [root]84.]
   1. Nap or down; flue[2]; soft, downy feathers.
      [1913 Webster]

   2. Hence: Anything light and downy, whose volume consists
      mostly of air, such as cotton or down.
      [PJC]

   3. Something light and inconsequential; something not to be
      taken seriously; -- used commonly of literary or dramatic
      productions, and sometimes of people.
      [PJC]

   4. A mistake, especially in the recitation of lines in a
      drama.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Fluff \Fluff\, v. t. & i.
   To make or become fluffy; to move lightly like fluff.
   --Holmes.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Fluff \Fluff\, v. t.
   To make a mistake in the performance of; -- used mostly of
   lines in a drama; as, he fluffed the last line of the act.
   [PJC]

WordNet (r) 3.0 (2006):

fluff
    n 1: any light downy material
    2: something of little value or significance [syn: bagatelle,
       fluff, frippery, frivolity]
    3: a blunder (especially an actor's forgetting the lines)
    v 1: make a mess of, destroy or ruin; "I botched the dinner and
         we had to eat out"; "the pianist screwed up the difficult
         passage in the second movement" [syn: botch, bodge,
         bumble, fumble, botch up, muff, blow, flub,
         screw up, ball up, spoil, muck up, bungle,
         fluff, bollix, bollix up, bollocks, bollocks up,
         bobble, mishandle, louse up, foul up, mess up,
         fuck up]
    2: erect or fluff up; "the bird ruffled its feathers" [syn:
       ruffle, fluff]
    3: ruffle (one's hair) by combing the ends towards the scalp,
       for a full effect [syn: tease, fluff]

Moby Thesaurus II by Grady Ward, 1.0:

163 Moby Thesaurus words for "fluff":
   Irish bull, aerate, air, anacoluthon, bad job, ball up, bevue,
   bloomer, blooper, blow, blubber, blunder, bobble, boggle, bollix,
   bonehead play, boner, boo-boo, boot, botch, breeze, bubble, bull,
   bungle, butter, catachresis, chaff, chip, clay, clumsy performance,
   cobweb, cock up, cork, cushion, daintiness, delicacy, dough, down,
   downiness, drop a brick, drop the ball, duff, dust, ease,
   eiderdown, error, ether, etourderie, fairy, feather, feather bed,
   feathers, filminess, fine-grainedness, fineness, fleece, floss,
   flub, flue, fluffiness, foam, folk etymology, foozle, foul up,
   froth, fuck up, fumble, fur, fuzz, fuzziness, gaucherie, gentle,
   girl friend, goof, goof up, gossamer, gossameriness,
   grammatical error, hash, howler, hypercorrection, hyperform, kapok,
   knead, lapse, laxate, limber, limber up, lint, loosen, louse up,
   malaprop, malapropism, marrowsky, mash, massage, mellow, mess,
   mess up, milden, miscue, mispronunciation, missaying, mistake,
   mistress, misusage, mollify, mote, muck up, muddle, muff, off day,
   peach fuzz, pile, pillow, plump, plush, pubescence, pudding, puff,
   puff up, pull a boner, pulp, putty, refinement, relax, rubber,
   ruin, sad work, satin, satininess, screw up, shake up, silk,
   silkiness, slip, smash, smoothness, snafu, soften, soften up,
   softness, solecism, spoil, sponge, spoonerism, spume, squash,
   straw, stumble, subdue, supple, swansdown, tenderize, thistledown,
   tone down, trip, tune down, velvet, velvetiness, wax, wool,
   zephyr