noun

1. a substance causing illness or death when eaten, drunk, or absorbed even in relatively small quantities
2. anything harmful or destructive to happiness or welfare, such as an idea, emotion, etc.
3. in a nuclear reactor, a substance, as boron, that readily absorbs thermal neutrons from a chain reaction, thereby decreasing the reactivity of a reactor core: it is used for safety or control
4. Chem. a substance that inhibits or destroys the activity of a catalyst, enzyme, etc. or that interferes with or checks a reaction

Etymology: OFr < L potio, potion

transitive verb

1. to give poison to; harm or destroy by means of poison
2. to put poison on or into
3. to influence wrongfully; corrupt to poison someone's mind

adjective