Standard Lemma guide

moonbat

adj · noun · 2 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

Each Play button uses your device's default local English voice, or a natural local fallback. The selected voice name appears after playback. This is synthesized speech, not a source recording.

  • /ˈmuːnˌbæt/

1

adj

Meaning 1

(of ideas) Absurd or obviously untruthful.

Definition source: English Wiktionary via Wiktextract

Usage: derogatory, informal

Topics: government, politics

Examples

  • 20204: The Bulwark Trump, who said last month at the Republican National Convention that he would never again retell the story of the attempt on his life “because it’s too painful to tell,” told that story with relish. He expounded at length on his usual moonbat fables about how countries around the world are emptying their prisons and mental institutions to send their convicts and lunatics to the United States.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

2

noun

Meaning 2

A liberal (someone with a left-wing ideology).

Definition source: English Wiktionary via Wiktextract

Usage: derogatory, informal

Topics: government, politics

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: leftard, libtard

Antonyms: none provided

History

Etymology

From moon + bat. Originally the name of the XP-67 experimental aircraft, developed by McDonnell Aircraft in 1941. Used in the 1940s by the science-fiction writer Robert Heinlein, then used in the term “barking moonbat” coined in 1999 by Perry de Havilland of “The Libertarian Samizdata”, a right-libertarian weblog. This originally referred to both left-wing and right-wing crazy people. Sometimes wrongly claimed to be a corruption of Monbiot (from George Monbiot, British environmentalist and Guardian columnist).