any of numerous species of flesh-eating or bloodsucking freshwater worms having a flattened segmented body with a sucker at each end: class Hirudinea

a person who leeches on another

archaic a physician or surgeon

Make each prescribe to other, as each other's leech — Shakespeare

in medicine, esp in former times, to use leeches to draw blood from (a patient) as a method of treatment

(often + on/off) to gain or seek to gain profit or advantage from another person, esp by clinging persistently

either vertical edge of a square sail

the rear edge of a fore-and-aft sail