lunatic
Americannoun
-
(no longer in technical use; now considered offensive) an insane person.
-
a person whose actions and manner are marked by extreme eccentricity or recklessness.
-
a person legally declared to be of unsound mind and who therefore is not held capable or responsible before the law: a former legal term.
adjective
-
(no longer in technical use; now considered offensive) insane.
-
characteristic or suggestive of lunacy; wildly or recklessly foolish.
-
Older Use. designated for or used by the insane.
a lunatic asylum.
-
gaily or lightheartedly mad, frivolous, eccentric, etc..
She has a lunatic charm that is quite engaging.
adjective
-
an archaic word for insane
-
foolish; eccentric; crazy
noun
Other Word Forms
Derived Forms
Etymology
Origin of lunatic
1250–1300; Middle English lunatik, from Old French lunatique, from Late Latin lūnāticus “moonstruck.” See Luna, -tic ( def. )
Explanation
A lunatic is someone who is either clinically insane or just acting really crazy. Someone driving too fast and zigging in and out of traffic is driving like a lunatic. The root of this word is luna, which means moon. That's because lunatic originally meant someone who went crazy with every phase of the moon, kind of like a werewolf. Most people these days don't believe in moon-caused insanity, but we still talk about lunatics, sometimes meaning clinically insane people. More often this is a slang term, used mainly in exaggerations, for anyone who seems wild and out of control.
Vocabulary lists containing lunatic
Did You Planet? Words With Surprisingly Spacey Origins
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
Harry Potter and the Prisoner of Azkaban
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
Twelfth Night
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
It was reminiscent for this viewer of 2008’s “Food Inc.,” which took a deep dive into the techniques of farmer Joel Salatin, the self-proclaimed “Christian libertarian environmentalist capitalist lunatic farmer.”
From The Wall Street Journal • Jun. 2, 2026
"The city is going to bear the scars of this lunatic for a really long time."
From Barron's • May 15, 2026
That Tomás, who has already survived the Great Hunger as well as a cruel workhouse, isn’t already a lunatic is perhaps less fantastical than the plot itself at times.
From Los Angeles Times • Jan. 30, 2026
Social media can efficiently make any lunatic theory an ineradicable and ever-evolving virus.
From The Wall Street Journal • Jan. 9, 2026
I focused on the light coming through the open doors, trying not to look at any faces, while I flew down the aisle like a lunatic.
From "The Line Tender" by Kate Allen
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
