# illegal

/ˌɪˈɫiɡəɫ/ (US) · /ɪlˈiːɡəl/ (UK)

Source: https://englishreference.com/word/illegal
Updated: 2026-06-19

## Senses

### 1. against the law

adjective · CEFR B1

not allowed by the law.

For teachers: contrary to, forbidden by, or not authorised by law, particularly criminal or civil statutes.

- It is illegal to drive a car without a valid license.
- 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. against the rules

adjective · CEFR B2

not allowed by the rules of a game or organization.

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

- The referee called a foul because the player made an illegal move.
- The athlete was disqualified for using an illegal substance that was strictly prohibited by the international sporting federation.

### 3. person without papers

noun · CEFR C1 · Informal · American English

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

For teachers: an individual residing in a country without official legal authorization or valid immigration documents.

- The news report discussed the challenges faced by illegals living in the city.
- The documentary explores the precarious lives of illegals who work in the agricultural sector without any social protections.

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

### 4. undercover spy

noun · CEFR C2 · Technical · Formal

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

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

- The agency spent years training the illegal to blend into the local community.
- The exchange of captured illegals took place on a bridge at midnight, following months of quiet diplomatic negotiations between the two rival nations.

## Examples

- It is illegal to park your car in front of a fire hydrant.
- The company faced heavy fines after the government discovered they were dumping illegal waste into the local river.
- While the moral implications were debated for years, the high court eventually ruled that the surveillance program was illegal under the current constitution.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.