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

If ever there was justification for an asterisk next to a record, his illegitimate assault on a scoring record is it.

From Los Angeles Times • Mar. 14, 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

With around 40% of births in the U.S. illegitimate, it’s easy to identify the problem but not so easy to correct it.

From The Wall Street Journal • Feb. 9, 2026

Maybe she had an illegitimate child, and her father— No. It’s Solomon she is crying for, not a baby.

From "Song of Solomon" by Toni Morrison

Related Words

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