This is the 7603rd most frequent Japanese word.
刻々
"刻々" means "moment by moment" or "constantly changing with time."
The term '刻々' here underscores the feeling of time steadily moving forward.
時間が刻々と過ぎていくのを感じた。
I felt time passing by moment by moment.
Here, '刻々' emphasizes the continuous and successive changes occurring in the situation.
事態は刻々と変化している。
The situation is changing moment by moment.
In this sentence, '刻々' is used to underline the gradual and progressive nature of a change in his expression.