without permission; without asking
Used when someone does something without obtaining prior consent or without giving notice. Often appears in negative contexts or as a set phrase.
He used my computer without asking.
It's rude to be absent without notice.
Negative continuative form of the verb 断る (ことわる, 'to refuse; to ask permission; to give notice'). Literally 'without refusing/asking/notifying', it has become a set expression meaning 'without permission'.