Source : Webster's Revised Unabridged Dictionary (1913)

used in medicine, as {Hirudo medicinalis} of Europe, and allied
species.

   Note: In the mouth of bloodsucking leeches are three
         convergent, serrated jaws, moved by strong muscles. By
         the motion of these jaws a stellate incision is made in
         the skin, through which the leech sucks blood till it
         is gorged, and then drops off. The stomach has large
         pouches on each side to hold the blood. The common
         large bloodsucking leech of America ({Macrobdella
         decora}) is dark olive above, and red below, with black
         spots. Many kinds of leeches are parasitic on fishes;
         others feed upon worms and mollusks, and have no jaws
         for drawing blood. See {Bdelloidea}. {Hirudinea}, and
         {Clepsine}.

   3. (Surg.) A glass tube of peculiar construction, adapted for
      drawing blood from a scarified part by means of a vacuum.

   {Horse leech}, a less powerful European leech ({H[ae]mopis
      vorax}), commonly attacking the membrane that lines the
      inside of the mouth and nostrils of animals that drink at
      pools where it lives.

Bloodsucker \Blood"suck`er\, n.
   1. (Zo["o]l.) Any animal that sucks blood; esp., the leech
      ({Hirudo medicinalis}), and related species.

   2. One who sheds blood; a cruel, bloodthirsty man; one guilty
      of bloodshed; a murderer. [Obs.] --Shak.

   3. A hard and exacting master, landlord, or money lender; an
      extortioner.

Source : WordNet®

Hirudo medicinalis
     n : large European freshwater leech formerly used for
         bloodletting [syn: {medicinal leech}]