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
Related Words
See illegal.
Other Word Forms
- illegitimacy noun
- illegitimately adverb
- illegitimateness noun
- illegitimation noun
Etymology
Origin of illegitimate
First recorded in 1530–40; il- 2 + legitimate
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.
And in a 1778 painting of Gainsborough’s wife, Margaret, who was the illegitimate daughter of a duke, he poses her classically in costly black lace.
From The Wall Street Journal • Mar. 4, 2026
The company says that it is “especially concerned about the use of A.I. to help individual humans or small groups gain unprecedented and illegitimate forms of concentrated power.”
From Slate • Feb. 25, 2026
Teenage parents and families of illegitimate children would respond, offering to pay them up to £15, approximately £2,300 in today's money.
From BBC • Feb. 9, 2026
Viewers eventually learn Sophie’s servitude is forced after her parentage is revealed — she’s the illegitimate daughter of an earl.
From Los Angeles Times • Jan. 29, 2026
At the end of his long life, Ser Piero did not forget how Leonardo came into the world: He cut his illegitimate son out of his will.
From "The Mona Lisa Vanishes" by Nicholas Day
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.
