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]