English Reference
adjective · noun

illegal

adj. · n.
US /ˌɪˈɫiɡəɫ/ UK /ɪlˈiːɡəl/ il·le·gal UK spelling illegals

  1. 01 B1 Intermediate Law

    adj.not allowed by the law.

    adj.contrary to, forbidden by, or not authorised by law, particularly criminal or civil statutes.

    Simple

    It is illegal to drive a car without a valid license.

    In context

    The company faced severe penalties after an investigation revealed they had been engaging in illegal dumping of toxic waste for years.

    Usage

    Commonly used as an attributive adjective before a noun or as a predicative adjective after a linking verb.

  2. 02 B2 Upper Intermediate Sport

    adj.not allowed by the rules of a game or organization.

    adj.forbidden by established rules or regulations within a specific non-legal context, such as sports or corporate policy.

    Simple

    The referee called a foul because the player made an illegal move.

    In context

    The athlete was disqualified for using an illegal substance that was strictly prohibited by the international sporting federation.

  3. 03 C1 Advanced InformalAmerican English

    n.a person who lives or works in a country without the correct legal documents.

    n.an individual residing in a country without official legal authorization or valid immigration documents.

    Simple

    The news report discussed the challenges faced by illegals living in the city.

    In context

    The documentary explores the precarious lives of illegals who work in the agricultural sector without any social protections.

    Teacher's tip

    This noun use is considered offensive by many people; 'undocumented immigrant' is the preferred neutral term in professional and academic contexts.

  4. 04 C2 Proficiency TechnicalFormal

    n.a spy who works in a foreign country without any official connection to their own government.

    n.an intelligence officer operating under deep cover in a foreign country without diplomatic immunity or official ties to their home state.

    Simple

    The agency spent years training the illegal to blend into the local community.

    In context

    The exchange of captured illegals took place on a bridge at midnight, following months of quiet diplomatic negotiations between the two rival nations.

    sleeper agentdeep cover agent

Usage illegal settlements · illegal under international · illegal outposts


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.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin legalis
Level B1 · Intermediate
Frequency Common
Updated