noun a virulent poison used in java and the adjacent islands for poisoning arrows. one kind, upas antiar, is, derived from upas tree (antiaris toxicaria). upas tieute is prepared from a climbing plant (strychnos tieute).
2. upas ·noun a tree (antiaris toxicaria) of the breadfruit family, common in the forests of java and the neighboring islands. its secretions are poisonous, and it has been fabulously reported that the atmosphere about it is deleterious. called also bohun upas.