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poison obtained from the castor-oil bean, 1888, from ricinus, genus name of the castor-oil plant (1694), from Latin ricinus (Pliny), of uncertain origin, perhaps the same word as ricinus "tick" (in sheep, dogs, etc.).
ricin ri·cin (rī'sĭn, rĭs'ĭn)
A poisonous protein that is extracted from the castor bean and is used as a biochemical reagent.