adverb
moment by moment; hour by hour; with each passing moment
Describes a situation that changes or progresses continuously as time passes, often with a sense of urgency or steady development.
状況は刻々に変化している。
The situation is changing moment by moment.
刻々に迫る締め切りに焦っている。
I'm panicking as the deadline approaches hour by hour.
Similar meaning 'moment by moment', but 刻一刻 is more literary and often used in formal contexts.
Reduplication of 刻 (こく, 'moment') with the adverbial particle に. The reading こっこく results from gemination (促音便) of the first く.