illegal meaning: definition, etymology and quotations

illegal

adj

UK /ɪˈliːɡəl/ · US /ɪˈli.ɡəl/

Etymology Borrowed from French illégal, from Medieval Latin illegalis, from Latin legalis, by surface analysis, il- + legal. In senses relating to immigration, via clipping of illegal alien or illegal immigrant.

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

4 more examples

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.a. 1654, John Selden, “Money”, in Table-Talk, 3rd edition, London: Jacob Tonson, published 1716, page 74:
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.2013 July 19, Peter Wilby, “Finland spreads word on schools”, in The Guardian Weekly, volume 189, number 6, archived from the original on 25 Mar 2022, page 30:
Major parties have long relied on large-scale campaign contributions, and the LDP was only recently mired in an illegal fundraising scandal. Sanseito drew its support from smaller, individual donations.2025 July 24, Ned Temko, “In Japan, too, voters want their country to be ‘great again’”, in The Christian Science Monitor, archived from the original on 27 Jul 2025:

Forbidden by established rules.

Moving a pawn backward is an illegal move in chess.
The computer program performed an illegal operation and was terminated.

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

Of an issue printed for collectors

Offensive, Sometimes, Of a person Being or doing something illegally.

illegal immigrant
illegal logger

1 more example

illegal pilot

US, Offensive, Sometimes Being an illegal immigrant; residing in a country illegally.

Derived terms: illegal alien, illegal combatant, illegal forward kick, illegal immigrant, illegal immigration, illegalisation, illegalise, illegalism, illegalist, illegalize, illegalness, illegal number, illegal prime

illegal

noun

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.c. 1650, John Spalding, The History of the Troubles and Memorable Transactions in Scotland, from the Year 1624 to 1645, volume II, Aberdeen: T. Evans, published 1792, pages 72–73:

Colloquial, In plural, As illegals Contraband, esp. illegal substances such as drugs.

…I've got illegals in my bottom…!2004, “Reapercussions”, in Dead Like Me, season 1, episode 4, spoken by Mason (Callum Blue):
“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.2008, J. D. Robb [pseudonym; Nora Roberts], Strangers in Death, Penguin, →ISBN:

Abbreviation, Colloquial, Ellipsis, Offensive Ellipsis of 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”.2024 August 1, Josh Halliday, Neha Gohil, “Police in England urged to protect mosques as far right plans more rallies”, in The Guardian, archived from the original on 24 Aug 2024:

Espionage, Government, Military, Politics, War 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.2012, Christopher Andrew, ‘Colder War’, Literary Review, number 399:
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.2022 August 26, Shaun Walker, “Socialite who charmed Nato staff in Naples was Russian spy, say investigators”, in The Guardian, archived from the original on 01 Oct 2022:

Synonyms: crimmigrant, illegal immigrant