Gri"son (?), n. [F., fr. grison gray, gray-haired, gris gray. See Gris.] (Zoöl.) (a) A South American animal of the family Mustelidae (Galictis vittata). It is about two feet long, exclusive of the tail. Its under parts are black. Also called South American glutton. (b) A South American monkey (Lagothrix infumatus), said to be gluttonous.