noun
dimwit; halfwit; slow-witted person
Derogatory term for a person who is slow on the uptake or foolish. Often used in casual, insulting speech.
あいつは本当にボケナスだな。
That guy is a real dimwit.
そんな簡単なこともわからないなんて、ボケナスかよ。
You can't even understand something that simple? What are you, a halfwit?
noun
faded, dull-colored eggplant
Original literal meaning; refers to an eggplant that has lost its color and freshness. Rarely used in modern conversation except in historical or explanatory contexts.
この茄子はもうボケナスになってしまった。
This eggplant has already become faded and dull.
Originally referred to a faded, dull-colored eggplant (惚け茄子). The derogatory sense for a slow-witted person likely arose from the image of a 'dull' or 'faded' eggplant, implying mental dullness.