The Collaborative International Dictionary of English v.0.48:

Biscuit \Bis"cuit\, n. [F. biscuit (cf. It. biscotto, Sp.
   bizcocho, Pg. biscouto), fr. L. bis twice + coctus, p. p. of
   coquere to cook, bake. See Cook, and cf. Bisque a kind of
   porcelain.]
   1. A kind of unraised bread, of many varieties, plain, sweet,
      or fancy, formed into flat cakes, and bakes hard; as, ship
      biscuit.
      [1913 Webster]

            According to military practice, the bread or biscuit
            of the Romans was twice prepared in the oven.
                                                  --Gibbon.
      [1913 Webster]

   2. A small loaf or cake of bread, raised and shortened, or
      made light with soda or baking powder. Usually a number
      are baked in the same pan, forming a sheet or card.
      [1913 Webster]

   3. Earthen ware or porcelain which has undergone the first
      baking, before it is subjected to the glazing.
      [1913 Webster]

   4. (Sculp.) A species of white, unglazed porcelain, in which
      vases, figures, and groups are formed in miniature.
      [1913 Webster]

   Meat biscuit, an alimentary preparation consisting of
      matters extracted from meat by boiling, or of meat ground
      fine and combined with flour, so as to form biscuits.
      [1913 Webster]

WordNet (r) 3.0 (2006):

biscuit
    n 1: small round bread leavened with baking-powder or soda
    2: any of various small flat sweet cakes (`biscuit' is the
       British term) [syn: cookie, cooky, biscuit]