Lewis & Short

būmastus, i (būmasta, ae, Edict. Diocl. p. 18), f., = βούμαστος, sc. ἄμπελος (having large breasts; cf. bumammus), a species of grape with large clusters, Verg. G. 2, 102 and Serv. ad loc.; id. Cul. 405; Col. 3, 2, 1; cf.: tument mammarum modo bumasti (acini), Plin. 14, 1, 3, § 15; 14, 3, 4, § 42.