“Poison” as a noun refers to a substance that can cause illness, injury, or death if ingested, inhaled, or absorbed. For example, arsenic is a well - known poison. medicine
As a verb, it means to administer poison to someone or something, or to contaminate or spoil something. For instance, “The water was poisoned by industrial waste” where the verb implies contamination. It can also be used metaphorically, like “His words poisoned her mind,” suggesting that the words had a harmful, corrupting influence.