illegal

adj

1. Contrary to, forbidden, or not authorized by law, especially criminal law.

   “This is illegal, you know!”

   “Nearly 40 million people live in UK areas with illegal air pollution”

   “Their illegal mining operations in Asia, Africa and elsewhere, are protected by officials and police paid to look the other way – and powerful customers in the construction industry who prefer not to ask too many questions.”

   “In all times the Princes in England have done ſomething illegal to get Money: But then came a Parliament and all was well, the People and the Prince kiſt and were Friends, and ſo things were quiet for a while.”

   “Imagine a country where children do nothing but play until they start compulsory schooling at age seven. Then, without exception, they attend comprehensives until the age of 16. Charging school fees is illegal, and so is sorting pupils into ability groups by streaming or setting.”

2. Forbidden by established rules.

   “Moving a pawn backward is an illegal move in chess.”

   “The computer program performed an illegal operation and was terminated.”

3. Totally fictitious, and often issued on behalf of a non-existent territory or country.
4. (offensive, sometimes)Being or doing something illegally.

   “illegal immigrant”

   “illegal logger”

   “illegal pilot”

5. (US, offensive, sometimes)Being an illegal immigrant; residing in a country illegally.

noun

1. (obsolete)An illegal act or technique.

   “That whatſoever illegals hath been uſed againſt his friends and ſubjects, by impriſoning them without law, or impoſing fines upon their eſtates, be diſclaimed, and that perſons ſo committed be forthwith diſcharged.”

2. (colloquial, in-plural)Contraband, esp. illegal substances such as drugs.

   “…I've got illegals in my bottom…!”

   ““Here’s what I could do,” Eve supposed. “I could slap your head against that wall, while I’m kicking your balls into your belly,” she added to the companion. “And after that, I can have you in restraints while I turn out your pockets. You’re carrying illegals.”

3. (colloquial, offensive)An illegal immigrant.

   “In Manchester and in Aldershot in Hampshire, asylum seeker accommodation was targeted by demonstrators carrying placards that read “deport them, don’t support them” and “no apartments for illegals”.”

4. A spy operating abroad illegally and under non-official cover, without visible ties to his or her country’s authorities.

   “Anna Chapman, whose glamorous appearance won her more publicity in the Western media than all the other illegals combined, was so successfully deceived by a US sting operation that she handed over her SVR laptop to an FBI agent posing as a Russian.”

   “Traditionally, illegals have been extremely hard for counterintelligence agencies to find, but in a world of biometric data, facial recognition software and open source investigation possibilities, it has become harder for Russia to keep its illegals below the radar.”