Merriam-Webster's Collegiate® Dictionary, 11th Edition
POISON
I. noun see: potion
Date: 13th century
1. a substance that through its chemical action usually kills, injures, or impairs an organism, b. something destructive or harmful, an object of aversion or abhorrence, a substance that inhibits the activity of another substance or the course of a reaction or process ,
II. transitive verb (poisoned; poisoning)
Date: 14th century
1. to injure or kill with poison, to treat, taint, or impregnate with or as if with poison, to exert a baneful influence on ; corrupt , to inhibit the activity, course, or occurrence of , poisoner noun
III. adjective
Date: circa 1520
poisonous , venomous , impregnated with poison ; poisoned