To commit adultery. / To pollute something; to adulterate.

An adulterer, especially a male one.

A fully grown human or animal. / A person who has reached the legal age of majority.

Fully grown. / Intended for or restricted to adults rather than children. / Containing material of an explicit sexual nature; of, or pertaining to, pornography. / Vulgar or profane.

(intransitive, informal) To behave like an adult. / (nonstandard, rare) To (cause to) be or become an adult.

(rare) Completely grown; mature.

simple past tense and past participle of adult

A predisposition towards adults (or a bias against children or other younger people).

simple past tense and past participle of adultize

Third-person singular simple present indicative form of adult