n. & v.
n. 1 a 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. a harmful influence or principle etc. 3 Physics & Chem. a substance that interferes with the normal progress of a nuclear reaction, chain reaction, catalytic reaction, etc.
v.tr. 1 administer poison to (a person or animal). 2 kill or injure or infect with poison. 3 infect (air, water, etc.) with poison. 4 (esp. as poisoned adj.) treat (a weapon) with poison. 5 corrupt or pervert (a person or mind). 6 spoil or destroy (a person's pleasure etc.). 7 render (land etc.) foul and unfit for its purpose by a noxious application etc. poison gas = GAS n. 4. poison ivy a n. American climbing plant, Rhus toxicodendron, secreting an irritant oil from its leaves. poison-pen letter an anonymous libellous or abusive letter. poisoner n. poisonous adj. poisonously adv.
[ ME f. OF poison, poisonner (as POTION) ]