1
: not allowed by the law : not legal
illegal [=illicit, unlawful] drugs
In this state, it is illegal for anyone under the age of 21 to drink alcohol.
an illegal alien/immigrant [=a foreign person who is living in a country without having official permission to live there]
2
: not allowed by the rules in a game
The team was penalized for an illegal play.
Cite this Entry
“Illegal.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/illegal. Accessed 29 Jun. 2026.
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