IUU

Adjective

illegal (comparative more illegal or (nonstandard or informal) illegaler, superlative most illegal or (nonstandard or informal) illegalest)

1. Contrary to, forbidden, or not authorized by law, especially criminal law.
   • This is illegal, you know!

   Synonyms:

   criminal, felonious, illicit, irregular, crimeful, illegitimate, lawbreaking, nonlawful, outlawed, unlawful

   Antonyms:

   lawful, legal, de jure, legitimate, licit, rightful

2. Forbidden by established rules.
   • Moving a pawn backward is an illegal move in chess.

   Synonyms:

   banned, disallowed, forbidden, impermissible, illicit, interdicted, nonallowed, nonlicet, prohibited, proscribed

3. Totally fictitious, and often issued on behalf of a non-existent territory or country.

   Synonyms:

   bogus

4. (offensive, sometimes) Being or doing something illegally.
   • illegal immigrant
5. (US, offensive, sometimes) Being an illegal immigrant; residing in a country illegally.

   Synonyms:

   undocumented

See all 8 meanings of illegal