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

As Sophie Baek, the illegitimate daughter of an earl who comes to work for the Bridgerton family, Ha’s wardrobe is often limited to a maid uniform. —Savannah Walsh, Vanity Fair, 3 Mar. 2026

As Sophie Baek, the Cinderella-style housemaid of illegitimate birth who charms the latest eligible Bridgerton bachelor, Ha is exquisite. —Kathryn Vanarendonk, Vulture, 27 Feb. 2026

After a whole season exploring the pains of being an illegitimate child and fears of pregnancy, Sophie and Benedict are now free to have children that would be welcomed warmly into society. —Jennifer Maas, Variety, 27 Feb. 2026

The most recent season featured Benedict Bridgerton (Luke Thompson) falling for maid and illegitimate child of nobility Sophie Baek (Yerin Ha) over the course of eight very Cinderella-esque episodes. —Marina Johnson, Louisville Courier Journal, 27 Feb. 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