Contrary to or in violation of a law Unlawful, illicit, criminal, felonious, wrongful, unauthorized, forbidden, illegitimate Not sanctioned by official rules (as of a game).
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Forbidden by law or statute.
See examples of illegal used in a sentence.
Not allowed by the rules of a sport An offensive word for someone… According to black's law dictionary (2nd edition), illegal may mean only that something lacks authority of the law or support from law (that is, that it's not legal), not that it's against the law, but that in ordinary usage it means a violation of the law. An illegal pass in football
Unacceptable to or not performable by a computer Discover everything about the word illegal in english Definition of illegal adjective in oxford advanced learner's dictionary Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.
There are six meanings listed in oed's entry for the word illegal, one of which is considered offensive
See ‘meaning & use’ for definitions, usage, and quotation evidence. (definition of illegal from the cambridge learner's dictionary © cambridge university press)