while someone is distracted; when their guard is down
トムはメアリーがお風呂に入ってる隙に、彼女の日記をこっそり読んだんだよ。
While Mary was taking a bath, Tom secretly read her diary.
犯人とその仲間は目を離した隙に逃げ出した。
The culprit and his accomplices escaped the moment we took our eyes off them.