illegitimate

American  

[il-i-jit-uh-mit, il-i-jit-uh-meyt] / ˌɪl ɪˈdʒɪt ə mɪt, ˌɪl ɪˈdʒɪt əˌmeɪt /

adjective

1. born of parents who are not married to each other; born out of wedlock.

   an illegitimate child.

2. not legitimate; not sanctioned by law or custom.

3. unlawful; illegal.

   an illegitimate action.

4. irregular; not in good usage.

5. Logic. not in accordance with the principles of valid inference.

6. Obsolete. (formerly, in London)

   1. 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.

   2. acting in or producing such productions.

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noun

1. a person recognized or looked upon as illegitimate.

verb (used with object)

illegitimated, illegitimating

1. to declare illegitimate.

illegitimate British  

/ ˌɪlɪˈdʒɪtɪmɪt /

adjective

1. born of parents who were not married to each other at the time of birth; bastard

2. forbidden by law; illegal; unlawful

3. contrary to logic; incorrectly reasoned

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noun

1. an illegitimate person; bastard

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

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.

Example Sentences

Hanna presented herself as a wealthy, illegitimate daughter of the sultan of Brunei, initially showering Hornigold, his then-partner Heather Kaniuk and his friends with lavish gifts, from cars to homes.

From BBC • Apr. 24, 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

Years of decay have left oil fields, pipelines and refineries in disrepair, with investors wary of sinking large sums and signing deals with a government led by Rodríguez that is widely viewed as illegitimate.

From The Wall Street Journal • Feb. 12, 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

Though it’s etymologically illegitimate, octopi is now so common that dictionaries list it as a second choice after octopuses.

From "Woe Is I" by Patricia T. O'Conner

Related Words

• illegal
• illicit
• improper
• invalid
• unauthorized
• unconstitutional
• unlawful