What does nutcase mean?
“Nutcase” is an informal noun for a person regarded as crazy, eccentric, or irrational. It is often used in a joking, mocking, or dismissive way, as in calling someone “a complete nutcase.” The word can describe unusual behaviour, extreme opinions, or an apparent lack of sound judgment, but its tone is usually derogatory rather than neutral. Because it labels a person as crazy or unreasonable, it may be insulting even when intended humorously. It is common in informal British and American English but is inappropriate in formal writing or sensitive professional situations.
A person regarded as crazy, eccentric, or irrational.
"He was called a nutcase after trying to explain his theory to everyone he met."
Informal and often derogatory; more appropriate in casual speech than in formal contexts.
Crazy, eccentric, or irrational in behaviour or outlook.
"That was a nutcase decision, and nobody could explain it."
Informal and usually mocking or dismissive.
The plural is formed by adding “-s.”
"They were convinced the neighbours were all nutcases."
“Nutcase” is a vivid, informal label for someone whose behaviour others regard as wildly eccentric or irrational.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does nutcase come from?
“Nutcase” is a compound formed from “nut” and “case.” The word “nut” has long been used informally to mean a person regarded as eccentric or crazy, while “case” intensifies the sense, suggesting someone who is an extreme or complete example. The compound is modern in origin and reflects the familiar British and American slang sense of “nut.”
Related word forms
How nutcase is actually used
Informal and commonly insulting or mocking. It is more typical in speech and casual writing than in formal or professional contexts, and can offend when directed at someone.
Easily confused with nutcase
“Nutcase” refers to a person considered crazy or eccentric, whereas “nut” can refer to a fruit, seed, or a person regarded as enthusiastic or eccentric.