The Collaborative International Dictionary of English v.0.48:
Leech \Leech\, n. [OE. leche, l[ae]che, physician, AS. l[=ae]ce;
akin to Fries. l[=e]tza, OHG. l[=a]hh[imac], Icel.
l[ae]knari, Sw. l[aum]kare, Dan. l[ae]ge, Goth. l[=e]keis,
AS. l[=a]cnian to heal, Sw. l[aum]ka, Dan. l[ae]ge, Icel.
l[ae]kna, Goth. l[=e]kin[=o]n.]
1. A physician or surgeon; a professor of the art of healing.
[Written also leach.] [Archaic] --Spenser.
Leech, heal thyself. --Wyclif (Luke
2. (Zool.) Any one of numerous genera and species of annulose
worms, belonging to the order Hirudinea, or Bdelloidea,
esp. those species 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
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.