illegal
adjective
uk/ɪˈliːɡəl/ us 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
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.