The Collaborative International Dictionary of English v.0.48:

Carp \Carp\, n.; pl. Carp, formerly Carps. [Cf. Icel. karfi,
   Dan. karpe, Sw. karp, OHG. charpho, G. karpfen, F. carpe, LL.
   carpa.] (Zool.)
   A fresh-water herbivorous fish (Cyprinus carpio.). Several
   other species of Cyprinus, Catla, and Carassius are
   called carp. See Cruclan carp.
   [1913 Webster]

   Note: The carp was originally from Asia, whence it was early
         introduced into Europe, where it is extensively reared
         in artificial ponds. Within a few years it has been
         introduced into America, and widely distributed by the
         government. Domestication has produced several
         varieties, as the leather carp, which is nearly or
         quite destitute of scales, and the mirror carp, which
         has only a few large scales. Intermediate varieties
         occur.
         [1913 Webster]

   Carp louse (Zool.), a small crustacean, of the genus
      Argulus, parasitic on carp and allied fishes. See
      Branchiura.

   Carp mullet (Zool.), a fish (Moxostoma carpio) of the
      Ohio River and Great Lakes, allied to the suckers.

   Carp sucker (Zool.), a name given to several species of
      fresh-water fishes of the genus Carpiodes in the United
      States; -- called also quillback.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Cyprinus carpio
    n 1: large Old World freshwater bottom-feeding fish introduced
         into Europe from Asia; inhabits ponds and sluggish streams
         and often raised for food; introduced into United States
         where it has become a pest [syn: domestic carp, Cyprinus
         carpio]