¦ adjective contrary to or forbidden by law.
¦ noun chiefly N. Amer. an illegal immigrant.
Derivatives
illegality noun (plural illegalities).
illegally adverb
Usage
Illegal and unlawful have slightly different meanings. Something that is illegal is against the law, whereas an unlawful act merely contravenes the rules that apply in a particular context. Thus handball in soccer is unlawful, but not illegal. A third word with a similar meaning is illicit: this tends to encompass things that are forbidden by custom or society, as in an illicit love affair.