(not) a single person; (no) one
Used with a negative verb to emphasize that absolutely no one does or is something. Stronger than simply saying 誰も.
See also: として
Not a single person believed his story.
No one was late for that meeting.
Standard kanji-kana mixed spelling.
Common variant with 誰 in kanji and ひとり in kana.
Variant with だれ in kana and 一人 in kanji.
Combination of 誰 (who) + 一人 (one person) + として (as, even), literally 'even as one person'. The phrase emphasizes the absence of any individual.