A substance that is harmful or lethal to a living organism.

“We used a poison to kill the weeds.”

Something that harms a person or thing.

“Gossip is a malicious poison.”

A drink; liquor.

“— I'll have a glass of whisky.”

To use poison to kill or paralyse (somebody).

“The assassin poisoned the king.”

To pollute; to cause to become poisonous.

“That factory is poisoning the river.”

To cause to become much worse.

“He poisoned the mood in the room with his non-stop criticism.”