Illegal
WordNet
adjective
(1) Prohibited by law or by official or accepted rules
"An illegal chess move"
WiktionaryText
Etymology
From il- + legal. In senses relating to immigration, via clipping from illegal alien or illegal immigrant.
Adjective
- Contrary to or forbidden by law, especially criminal law.
- Not permitted by rules
- Moving a pawn backward is an illegal move in chess.
- Totally fictitious, and often issued on behalf of a non-existent territory or country.
- Being an illegal immigrant; residing in a country illegally.