illegal il‧le‧gal [ɪˈliːgl] adjective
1. LAW not allowed by the law:
illegal it is illegal to do something

• It's illegal to copy copyrighted movie cassettes.

• Despite knowing about the illegal activity, the executives failed to tell the government for months.

• He made illegal payments in connection with contracts awarded to his company.

— illegally adverb :

• An investigation is being conducted to see if anyone illegally profited from the takeover.

2. COMPUTING involving an instruction, character etc that is not allowed in a particular computer program

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illegal UK US /ɪˈliːgəl/ adjective
LAW not allowed by law: »

According to state law, smoking is illegal in all public buildings.

illegal (for sb) to do sth »

It is illegal for a company to force an employee into early retirement.

make sth illegal »

The new law will make it illegal to record phone conversations without consent.


illegal sales/profits/trades

Compare LEGAL(Cf. ↑legal)
IT used to describe a character (= letter, number, or symbol) that you cannot use in a particular place on a computer, because it may create problems: »

The colon is the only illegal character for file and folder names.

illegally adverb

Approximately 500,000 workers enter the country illegally each year.

Financial and business terms. 2012.