A very short span of time; in the blink of an eye (often used as またたく間に).
彼の人気は瞬く間に広まり、テレビ出演が続いた。
His popularity spread in no time, and he kept appearing on TV.
またたく間に夕方になって、店は閉店の準備を始めた。
In the blink of an eye it was evening, and the store began preparing to close.
問題は瞬く間に解決したので、みんな驚いた。
The problem was solved in an instant, so everyone was surprised.