insane
UK: ɪnˈseɪn | US: ɪnˈseɪn
adj. mentally ill or unstable
adj. extremely foolish or irrational
adj. wildly extravagant or intense
The word "insane" originates from Latin insanus, combining in- (a negative prefix meaning "not") and sanus ("healthy" or "sound"). Initially, it described a literal lack of mental health, but over time, its meaning expanded to include extreme irrationality or foolishness. The morpheme sane persists in modern English (e.g., "sanity"), while in- remains a common negating prefix. The evolution reflects societal shifts in understanding mental health, broadening from clinical to colloquial usage.
The court ruled that the defendant was legally insane at the time of the crime.
Spending $1,000 on a coffee mug is just insane.
The crowd erupted into insane cheers when the team scored.
His insane work schedule left him exhausted.
The idea of jumping off a cliff for fun sounds insane to me.