illegal

American  

[ih-lee-guhl] / ɪˈli gəl /

adjective

1. forbidden by law or statute.

   Synonyms:

   unlicensed, illicit, illegitimate, unlawful

2. contrary to or forbidden by official rules, regulations, etc..

   The referee ruled that it was an illegal forward pass.

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noun

1. Informal: Disparaging and Offensive. illegal alien.

illegal British  

/ ɪˈliːɡəl /

adjective

1. forbidden by law; unlawful; illicit

2. unauthorized or prohibited by a code of official or accepted rules

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noun

1. a person who has entered or attempted to enter a country illegally

Sensitive Note

See illegal alien.

Synonym Usage

Illegal, unlawful, illegitimate, illicit, criminal can all describe actions not in accord with law. Illegal refers most specifically to violations of statutes or, in organized athletics, codified rules: an illegal seizure of property; an illegal block ( in football ). Unlawful means not sanctioned by or according to law: an unlawful claim to the inheritance; to take unlawful advantage of the trading situation. Illegitimate means lacking legal or traditional right or rights: an illegitimate child; illegitimate use of privileged knowledge. Illicit, which originally meant simply “not permitted,” now most often applies to matters regulated by law with specific emphasis on the way things are carried out: illicit conversion of property; an illicit attempt to control the market. Criminal most often refers to violation of the statutes of penal as opposed to civil law. All felonies are criminal as are all crimes sometimes punishable by death such as murder, arson, and kidnapping: a criminal act.

Other Word Forms

• illegality
  noun
• illegally
  adverb

Etymology

Origin of illegal

From the Medieval Latin word illēgālis, dating back to 1620–30. See il- ², legal

Compare meaning

How does illegal compare to similar and commonly confused words? Explore the most common comparisons:

• unlawful vs. illegal
• illicit vs. illegal
• undocumented vs. illegal

Explanation

Something illegal is against the law or breaks the rules. If you're reading this in jail, you've probably done something illegal, and if you're not in jail, there's plenty of time to obey the law. You can use the adjective illegal to describe breaking the rules, as when you head-butt someone in a game. Acts that go against the law, such as robbing a bank, are also illegal. There is a wide range of things called illegal, from small acts to big ones, but no matter the seriousness, if it is against the law, it is illegal. This adjective also describes people who enter countries without official government approval, they are called "illegal immigrants" or "illegal aliens."

Example Sentences

Fifteen countries signed a global declaration on Wednesday aimed at combating illegal and destructive fishing with better data.

From Barron's • Jun. 17, 2026

Although fishing for totoaba was banned decades ago, illegal harvesting continues due to wildlife trafficking networks and persistent overseas demand.

From Science Daily • Jun. 17, 2026

But it’s illegal to keep a deer as a personal possession, according to the Department of Fish and Wildlife.

From Los Angeles Times • Jun. 16, 2026

While the people who answer these phone lines are required to report any illegal behavior they hear about, this can be hard to do because the helplines offer complete anonymity to the person calling.

From Slate • Jun. 15, 2026

It was illegal to bring all this Western loot into the Soviet Union, but Penkovsky breezed through customs without a search—the goodies were for his bosses, and they made sure he wasn’t bothered.

From "Fallout: Spies, Superbombs, and the Ultimate Cold War Showdown" by Steve Sheinkin

Related Words

• banned
• criminal
• illegitimate
• illicit
• irregular
• outlawed
• prohibited
• smuggled
• unauthorized
• unconstitutional
• unlawful
• unlicensed
• unwarranted
• wrongful