The Collaborative International Dictionary of English v.0.48:

Frost \Frost\, v. t. [imp. & p. p. Frosted; p. pr. & vb. n.
   Frosting.]
   1. To injure by frost; to freeze, as plants.
      [1913 Webster]

   2. To cover with hoarfrost; to produce a surface resembling
      frost upon, as upon cake, metals, or glass; as, glass may
      be frosted by exposure to hydrofluoric acid.
      [1913 Webster]

            While with a hoary light she frosts the ground.
                                                  --Wordsworth.
      [1913 Webster]

   3. To roughen or sharpen, as the nail heads or calks of
      horseshoes, so as to fit them for frosty weather.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Frosting \Frost"ing\, n.
   1. A composition of sugar and beaten egg, used to cover or
      ornament cake, pudding, etc.
      [1913 Webster]

   2. A lusterless finish of metal or glass; the process of
      producing such a finish.
      [1913 Webster]

   3. the lightened color on part of an object, as of hair,
      produced by treatment with bleach or other chemicals; as
      only part of the object is thus treated, the final color
      of the object is two-toned; also, the process of producing
      such a two-toned effect.
      [PJC]

WordNet (r) 3.0 (2006):

frosting
    n 1: a flavored sugar topping used to coat and decorate cakes
         [syn: frosting, icing, ice]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "frosting":
   Jell-O, albification, blanching, blancmange, bleaching, candy,
   comfit, compote, confiture, conserve, etiolation, gelatin, glaze,
   grizzling, honey, icing, jam, jelly, marmalade, meringue, mousse,
   preserve, silvering, sweet, sweet stuff, sweetmeat, sweets,
   topping, tutti-frutti, whipped cream, whitening, whitewashing