Poison  —n. 1 substance that when introduced into or absorbed by a living organism causes death or injury, esp. One that kills by rapid action even in a small quantity. 2 colloq. Harmful influence. —v. 1 administer poison to. 2 kill, injure, or infect with poison. 3 treat (a weapon) with poison. 4 corrupt or pervert (a person or mind). 5 spoil or destroy (a person's pleasure etc.).  poisoner n. Poisonous adj. [latin: related to *potion]