expression, na-adjective
gushing forth; bursting out; like breaking a dam
Idiomatic expression describing something that suddenly flows or bursts out in large amounts, like water from a broken dam. Often used for emotions, words, tears, or crowds. The literal image is of a dam breaking.
彼女は堰を切ったように泣き出した。
She burst into tears as if a dam had broken.
観客が堰を切ったようにスタジアムになだれ込んだ。
The spectators poured into the stadium like a flood.
どっと is an adverb for a sudden burst of sound, laughter, or movement, while 堰を切ったよう emphasizes the uncontrollable, dam-breaking nature of the outflow.
一気に means 'in one go' or 'all at once', focusing on speed and continuity, whereas 堰を切ったよう highlights the sudden release after being pent up.
From the image of a dam (堰) breaking (切った) and water gushing out. The phrase is used figuratively to describe a sudden, unstoppable outpouring.