Source : Webster's Revised Unabridged Dictionary (1913)

Lamprey \Lam"prey\, n.; pl. {Lampreys}. [OE. lampreie, F.
   lamproie, LL. lampreda, lampetra, from L. lambere to lick +
   petra rock, stone. The lampreys are so called because they
   attach themselves with their circular mouths to rocks and
   stones, whence they are also called {rocksuckers}. See {Lap}
   to drink, {Petrify}.] (Zo["o]l.)
   An eel-like marsipobranch of the genus {Petromyzon}, and
   allied genera. The lampreys have a round, sucking mouth,
   without jaws, but set with numerous minute teeth, and one to
   three larger teeth on the palate (see Illust. of
   {Cyclostomi}). There are seven small branchial openings on
   each side. [Written also {lamper eel}, {lamprel}, and
   {lampron}.]

Source : WordNet®

lamprey
     n : primitive eellike freshwater or anadromous cyclostome having
         round sucking mouth with a rasping tongue [syn: {lamprey
         eel}, {lamper eel}]