also: あっとゆうま · あっとゆーま
expression, noun
an instant; a split second; no time at all
Used to describe something happening extremely quickly, often in the phrase あっという間に (in the blink of an eye). The literal meaning is 'the time it takes to say ah!'.
See also: あっと言う間に
あっという間に夏休みが終わった。
Summer vacation was over in the blink of an eye.
He solved the problem in no time at all.