The Collaborative International Dictionary of English v.0.48:

Mousse \Mousse\ (m[=oo]s), n. [F.]
   1. (Cookery) A frozen dessert of a frothy texture, made of
      sweetened and flavored whipped cream, sometimes with the
      addition of egg yolks and gelatin. Mousse differs from ice
      cream in being beaten before -- not during -- the freezing
      process.
      [Webster 1913 Suppl.]

   2. Any of a variety of foods whipped to a light texture; as,
      a salmon mousse.
      [PJC]

   3. A foam containing special chemicals, used for styling
      hair.
      [PJC]

WordNet (r) 3.0 (2006):

mousse
    n 1: a rich, frothy, creamy dessert made with whipped egg whites
         and heavy cream
    2: a light creamy dish made from fish or meat and set with
       gelatin
    3: toiletry consisting of an aerosol foam used in hair styling
       [syn: mousse, hair mousse, hair gel]
    v 1: apply a styling gel to; "she mousses her hair" [syn:
         mousse, gel]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "mousse":
   Charlotte, Jell-O, blancmange, breakers, candy, carrot pudding,
   chocolate mousse, collar, comfit, compote, confection,
   confectionery, confiture, conserve, custard, duff, flan, foam,
   frosting, froth, gelatin, glaze, head, honey, icing, jam, jelly,
   junket, lather, marmalade, meringue, offscum, plum pudding,
   preserve, pudding, puff, rennet, scud, scum, sea foam, soapsuds,
   souffle, spindrift, spoondrift, spray, spume, steamed pudding,
   stinging, suds, surf, sweet, sweet stuff, sweetmeat, sweets,
   syllabub, tapioca pudding, trifle, tutti-frutti, vanilla pudding,
   whipped cream, white water