Colloquial and derogatory term for a stupid, careless, or absent-minded person. Often used teasingly or in mild insults.
That guy is a real dimwit.
Making such a simple mistake, you're beyond a blockhead.
Standard kanji spelling.
Variant spelling without okurigana.
Mixed katakana-kanji spelling, occasionally seen in informal writing.
Derived from the verb 抜ける (nukeru, 'to come out, to be missing') and 作 (saku, a common suffix in names and derogatory terms). The combination suggests someone who is 'missing' something, i.e., lacking intelligence or common sense.