Definition of poison:
any substance that causes injury or illness or death of a living organism
anything that harms or destroys; "the poison of fascism"
spoil as if by poison; "poison someone's mind"; "poison the atmosphere in the office"
kill with poison; "She poisoned her husband"
add poison to; "Her husband poisoned her drink in order to kill her"
kill by its poison; "This mushrooms can poison"
administer poison to; "She poisoned her husband but he did not die"