Nutso

Part of speech: adjective

Pronunciation: /ˈnʌ.t͡soʊ/

Definitions

1. Showing an extreme level of unpredictability or oddity in behavior
2. Displaying a mindset that radically diverges from typical mental stability or rationality
3. Exhibiting wildly unusual or bizarre conduct that stands out from normal behavior

Etymology: "Nutso" is simply "nuts" with the suffix "-o" tacked onto the end. The base word "nuts," meaning crazy or insane, has been slang in English since the early 1900s, and the "-o" ending belongs to a family of informal American slang formations such as "wino," "lefto," and "weirdo." Attaching "-o" to an adjective or noun creates a casual, somewhat jocular label for a person or state, and "nutso" follows that pattern exactly. The suffix does most of the work of making the word feel lighthearted. Where "nuts" simply says someone has lost their wits, "nutso" adds a playful, almost cartoonish tone, which is why it sounds at home in comic dialogue and everyday teasing. The word functions here as an adjective describing someone who is completely mentally unbalanced.

Synonyms: crazy, insane, mad, loony

Antonyms: sane, rational