illegitimate

adjective

il·​le·​git·​i·​mate ˌi-li-ˈji-tə-mət 

1

a

: not recognized as lawful offspring

b

: born of parents not married to each other

2

a

: not sanctioned by law : illegal

an illegitimate government

… a retaliatory, harassing, or other illegitimate motive.

—Diamond "D" Const. Corp. v. McGowan, 282 F. 3d 191 (2002)

b

: not authorized by good usage

c

of a taxon : published but not in accordance with the rules of the relevant international code

3

: not reasonable or fair

were fired for illegitimate reasons

4

: not rightly deduced or inferred : illogical

5

: departing from the regular : erratic

illegitimately adverb

Synonyms of illegitimate

• spurious
• misbegotten
• supposititious
• adopted
• natural
• orphaned

Examples of illegitimate in a Sentence

She thinks that my concerns are illegitimate.

They were fired from their jobs for illegitimate reasons.

Recent Examples on the Web

The show followed the destitute Cuylers — father Early, his illegitimate son Rusty, his meth-loving sister Lily, and his crabby grandmother Granny — and their various moneymaking high jinks. —Eric Vilas-Boas, Vulture, 18 Mar. 2026

But then a mysterious Romany woman (Rebecca Ferguson) turns up, and persuades him to return to Birmingham, in order to bring his violent illegitimate son (Barry Keoghan) – who now runs his Peaky Blinders mob – to heel. —The Week Uk, TheWeek, 12 Mar. 2026

In statements to ProPublica, the credit bureaus said that many complaints are illegitimate, including a large volume filed by credit repair organizations that charge customers to challenge negative information on their reports. —Joel Jacobs, CNN Money, 11 Mar. 2026

In a July public comment letter, Experian argued it should not be required to respond to individual CFPB complaints and that the vast majority of those filed recently are illegitimate. —Joel Jacobs, ProPublica, 10 Mar. 2026

Word History

First Known Use

1536, in the meaning defined at sense 1a

Rhymes for illegitimate

• legitimate

Kids Definition

illegitimate

adjective

il·​le·​git·​i·​mate ˌil-i-ˈjit-ə-mət 

1

: born of a father and mother who are not married

2

: illegal

illegitimately adverb

Legal Definition

illegitimate

adjective

il·​le·​git·​i·​mate ˌi-li-ˈji-tə-mət 

1

: not recognized by the law as offspring

specifically : born out of marriage

Note: An illegitimate child is usually legitimated by his or her parents' later marriage. Illegitimate children generally have the same inheritance rights under intestate successions as legitimate children; statutes limiting their inheritance rights have been found to violate the equal protection clause.

2

: not valid according to law

illegitimate noun