lunatic

1 of 2

noun

lu·​na·​tic ˈlü-nə-ˌtik 

plural lunatics

1

dated, now offensive : someone affected with a severely disordered state of mind

2

informal : a person who behaves in a wildly foolish, reckless, or uncontrolled manner

lunatic

2 of 2

adjective

1

a

dated, now offensive : affected with a severely disordered state of mind

b

dated, now offensive : providing care to mentally ill people

a lunatic asylum

2

informal : wildly foolish

a lunatic idea

lunatic behavior

Synonyms

Adjective

• balmy
• barmy [chiefly British]
• bats
• batty
• bedlam
• bonkers
• brainsick
• bughouse [slang]
• certifiable
• crackbrained
• cracked
• crackers
• crackpot
• cranky [dialect]
• crazed
• crazy
• cuckoo
• daffy
• daft
• demented
• deranged
• fruity [slang]
• gaga
• haywire
• insane
• kooky
• kookie
• loco [slang]
• loony
• looney
• loony tunes
• looney tunes
• mad
• maniacal
• maniac
• mental
• meshuga
• meshugge
• meshugah
• meshuggah
• moonstruck
• non compos mentis
• nuts
• nutty
• psycho
• psychotic
• scatty [chiefly British]
• screwy
• unbalanced
• unhinged
• unsound
• wacko
• whacko
• wacky
• whacky
• wud [chiefly Scottish]

Examples of lunatic in a Sentence

Adjective

He hatched a lunatic plot to overthrow the government.

another of his lunatic ideas

Recent Examples on the Web

Adjective

With his shock of spiky hair and adrenaline rushes, Smith turns a corporate villain into a lunatic new-wave frontman. —Charles McNultytheater Critic, Los Angeles Times, 30 Jan. 2023

The first personality is the lunatic, chaotic artist, with no limits. —John Bleasdale, Variety, 8 Dec. 2022

In an idyllic cabin in the woods, a deaf author named Maddie is trying out new recipes, avoiding her ex-boyfriend's phone calls, and trying to combat writer's block, all while a crazed lunatic waits to strike. —K. Thor Jensen, PCMAG, 20 Oct. 2022

One small exchange, one ship sunk for another, would become a lunatic conflagration. —Ian McEwan, The New Yorker, 1 Aug. 2022

Word History

Etymology

Noun

Middle English lunatik, borrowed from Anglo-French lunatic, borrowed from Late Latin lūnāticus, noun derivative of Latin lūnāticus "suffering from a mental or neurological disorder allegedly affected by the phases of the moon" — more at lunatic entry 2

Adjective

Middle English lunatik "suffering from a recurrent mental or neurological disorder," borrowed from Anglo-French lunatic, borrowed from Latin lūnāticus "suffering from a mental or neurological disorder allegedly affected by the phases of the moon," from lūna "moon" + -āticus, adjective suffix of appurtenance — more at lunar, -age

Note: The word is unattested in classical Latin aside from the legal treatises of Julius Paulus (2nd-3rd centuries a.d.). The derivation was perhaps modeled on fānāticus "inspired by orgiastic rites, fanatic entry 2." Compare Greek (New Testament) selēniázesthai, taken to mean "to suffer from seizures," a derivative of selḗnē "moon."

First Known Use

Noun

14th century, in the meaning defined at sense 1

Adjective

14th century, in the meaning defined at sense 1a

Phrases Containing lunatic

• lunatic fringe

Kids Definition

lunatic

1 of 2 adjective

lu·​na·​tic

ˈlü-nə-ˌtik

1

a

: mentally unsound

—used chiefly in the past

b

: designed for the care of mentally ill people

lunatic asylum

—used chiefly in the past

2

: wildly foolish

a lunatic idea

lunatic

2 of 2 noun

: a mentally ill person

—used chiefly in the past

Medical Definition

lunatic

noun

lu·​na·​tic ˈlü-nə-ˌtik 

dated, now offensive : an individual marked by a severely disordered state of mind

Legal Definition

lunatic

noun

lu·​na·​tic

ˈlü-nə-tik

: an insane person

—used especially formerly

lunatic adjective