Tris"to*ma (?), n. [NL., from Gr. (see Tri-) + mouth.] Zool.
Any one of numerous species of trematode worms belonging to Tristoma and allied genera having a large posterior sucker and two small anterior ones. They usually have broad, thin, and disklike bodies, and are parasite on the gills and skin of fishes.
© Webster 1913.