illegitimate
Americanadjective
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born of parents who are not married to each other; born out of wedlock.
an illegitimate child.
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not legitimate; not sanctioned by law or custom.
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unlawful; illegal.
an illegitimate action.
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irregular; not in good usage.
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Logic. not in accordance with the principles of valid inference.
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Obsolete. (formerly, in London)
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of or relating to stage plays in which musical numbers were inserted because of laws that gave only a few theaters the exclusive right to produce straight dramas.
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acting in or producing such productions.
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noun
verb (used with object)
adjective
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born of parents who were not married to each other at the time of birth; bastard
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forbidden by law; illegal; unlawful
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contrary to logic; incorrectly reasoned
noun
Synonym Usage
See illegal.
Other Word Forms
Etymology
Origin of illegitimate
First recorded in 1530–40; il- 2 + legitimate
Explanation
Something illegitimate is unlawful, or improper. If you're a doctor, even a great doctor, but you were never certified by the medical board, then you're an illegitimate doctor. Illegitimate has the root for "law" in it, and something illegitimate is outside the law or custom. A child not born to married parents is known as an illegitimate child, although so many people are making different choices about how to raise families, that the stigma is dropping away, especially if the child isn't the result of philandering (cheating). In King Lear, Edmund is mad that he's an illegitimate son, because it means he can't inherit the throne.
Vocabulary lists containing illegitimate
Black Like Me
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leg, legis
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leg, legis (law)
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
He annulled her royal title; declared their only child, Elizabeth, illegitimate; and damned her memory.
From The Wall Street Journal ● Aug. 22, 2026
The paper says an international hunt is under way for the hoaxer responsible for the security breach during which Burnham thought he was sending messages to Susie Wiles "before becoming suspicious the contact was illegitimate".
From BBC ● Aug. 18, 2026
At the end of April, the group said it had reinstated a regional parliament, which had been deemed illegitimate.
From Barron's ● Aug. 11, 2026
Most important, she outmaneuvered the Texas judge by quashing the subpoena itself, finding that it was an illegitimate and unconstitutional invasion of privacy.
From Slate ● May 19, 2026
“Though it’s been rumored there are some illegitimate ones.”
From "Crispin: The Cross of Lead" by Avi
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
