Numbnuts American offensive slang
The phrase is derogatory, and sometimes humorous. It is often used as a term of address.
Used to say that somebody is an idiot or a stupid person
Don't ask him this question. He's such a numbnut.
Some numbnuts left the tap running in the bathroom and there's water everywhere.
Put your hand here, numbnut!
Extremely stupid
Very stupid, or silly
Stupid or crazy
(n): a fool person,
(adj): stupid, foolish, silly
He is rich but also stupid.
Green’s Dictionary of Slang traces the use of "numbnuts", meaning “idiot” when used as a term of address, back to 1969. The term is a natural evolution from the term "numb head", which has been in use since the 18th century.