adverb
(not) in the least; (not) at all; (not) a bit
Always used with a negative predicate to emphasize complete absence or denial. Stronger than 全然 or 少しも.
彼の話には毛頭興味がない。
I have not the slightest interest in his story.
そんなつもりは毛頭ありません。
I have absolutely no such intention.
Compound of 毛 (け, 'hair; tiny amount') and 頭 (とう, 'head; top'), literally 'even a hair's tip', used figuratively to mean 'not even a tiny bit'. The exact historical derivation is uncertain, but the spelling is conventionally associated with this emphatic negative meaning.