loony

Someone who's loony is nutty or wacky — it's a slang term for "crazy." Your loony aunt Mabel might prefer wearing a teddy bear costume when she goes to the grocery store.

Loony is an informal, derogatory term for mentally ill, but it can also mean silly or outrageous. You could say, "My parents are loony — they call me three times a day and are always sending me photos of their little dog dressed in doll clothes," or talk about the loony story you read for your book group. Loony is an American-coined word, short for lunatic and also referencing the cry of the bird called a loon.

Definitions of loony
1

adj informal or slang terms for mentally irregular

Synonyms:
around the bend, balmy, barmy, bats, batty, bonkers, buggy, cracked, crackers, daft, dotty, fruity, haywire, kookie, kooky, loco, loopy, nuts, nutty, round the bend, wacky, whacky
insane
afflicted with or characteristic of mental derangement

n someone deranged and possibly dangerous

Synonyms:
crazy, looney, nutcase, weirdo
Type of:
lunatic, madman, maniac
an insane person

Sign up, it's free!

Whether you're a student, an educator, or a lifelong learner, Vocabulary.com can put you on the path to systematic vocabulary improvement.