Noun
numbnuts (plural numbnuts or numbnutses)
(chiefly US, slang, derogatory, sometimes humorous, often as a term of address) A slow-witted, unresponsive, or inept person (usually male).
Tell numbnuts over there to wake up and pay attention to his work.
It was sort of like seeing that annoying work colleague tumble and fall comically in the office… Only to realise that the numbnuts knocked over your lunch while they were at it! Source: Internet
He again flipped me off as if to say, “Like I’m gonna listen to a numbnuts NFO.” Source: Internet