adj
loony
LOO-nee
adj
1
Crazy or mentally unstable.
"That's a completely loony idea."
"He went a bit loony after weeks without sleep."
2
Extremely silly or ridiculous.
"The plot of the movie was loony but fun."
noun
1
An informal word for a foolish or unstable person.
"Only a loony would try to cross that river in a storm."
How to Use Loony
Learner’s notesIn plain EnglishCrazy, silly, or someone acting that way — used casually, often affectionately.
When to use it
Informal; can sound insensitive when applied to real mental illness, so it's mostly used for silly behaviour or ideas rather than clinical conditions.
Word Forms
loonier comparative, loonies plural, looniest superlative
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Etymology
A shortened, informal version of "lunatic."