(archaic) The snipping off the tail of a leech engaged in sucking human blood, in order to let the blood run out of it and so increase its powers of drawing blood.
Etymology
Irregularly formed as Ancient Greekβδέλλᾰ(bdélla, “leech”) + -tomy (from -τοµία(-toµía, “a cutting”); from τέμνω(témnō, “I cut”); the etymological spelling is bdellotomy.