English Reference

Word

illegitimate

Phoneticsil·le·git·i·mate

US/ˌɪɫɪˈdʒɪtəmɪt/

UK/ɪlədʒˈɪtɪmət/

Definitions

01not legal

B2 · Law

adj. not allowed by the law or by official rules.

adj. not in accordance with the law or established legal standards.

“The court ruled that the government's use of power was illegitimate.”

“The opposition party argued that the election results were illegitimate due to widespread reports of voter intimidation.”

02born to unmarried parents

C1

adj. born to parents who were not married to each other.

adj. born of parents not lawfully married to each other at the time of birth.

“In the past, being an illegitimate child could cause many social problems.”

“The historical novel focuses on the struggles of an illegitimate son trying to claim his rightful inheritance from a noble family.”

Formal

Usage

In modern legal and social contexts, this term is often replaced by 'born out of wedlock' or simply avoided due to its historical stigma.

Teaching tip

This sense is historically significant but can be offensive in modern conversation; students should use it only when discussing history or law.

Synonyms

Antonyms

03not logical

C1

adj. not following the rules of logic or clear thinking.

adj. not correctly deduced or inferred according to the principles of logic.

“That is an illegitimate conclusion because it is not based on the facts.”

“The professor pointed out that the student's argument relied on an illegitimate inference that ignored the primary data set.”

Academic

Antonyms

04botany

C2 · Science

adj. a technical term for how certain flowers are fertilized.

adj. referring to the fertilization of pistils by stamens of a different length in heterostylous plants.

“The scientist studied the illegitimate pollination of the primrose flowers.”

“Illegitimate crosses in trimorphic species often result in significantly reduced seed production compared to legitimate pairings.”

Technical

Antonyms

05a person

C2

n. an old-fashioned and often rude way to describe a person born to unmarried parents.

n. a person born to parents who are not married to each other.

“The king had several children, but only one was not an illegitimate.”

“Under the old laws of the realm, an illegitimate could not inherit the crown regardless of their father's wishes.”

Archaic · Formal

Teaching tip

This noun form is extremely rare in modern English and is usually replaced by the adjective phrase 'illegitimate child'.

Synonyms

06to make invalid

C2 · Law

v. to make something no longer legal or official.

v. to render something illegitimate or to declare it as lacking legal status.

“The new law might illegitimate many existing contracts.”

“The decree served to illegitimate the previous administration's treaties, causing a diplomatic crisis.”

Formal

Real-World Examples

“The former ambassador argues that the current president, Min Aung Hlaing, the general who plunged Myanmar into conflict and economic chaos, is illegitimate and had no power to ask him to leave the property.”
The Guardian · 12 Aug 2026
“The news website reported that officials said Burnham communicated with the person claiming to be Susie Wiles "before becoming suspicious that the contact was illegitimate" and claimed only a "few messages" were exchanged.”
BBC News · 17 Aug 2026

Etymology

First attested in 1536, from Latin illēgitimus, most likely an adapted borrowing of Middle French illegitime, equivalent to il- + legitimate, see -ate (etymology 1, 2 and 3).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Domain

Botany

This entry

Level
C1 · Advanced
Frequency
Frequent
Updated

Scan code

englishreference.com/q/illegitimate

English Reference