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.
She burst into tears as if a dam had broken.
The spectators poured into the stadium like a flood.
Standard kanji-kana mixed spelling. 堰 means 'dam' or 'weir'.
Kana spelling is common when the kanji 堰 is considered difficult or unnecessary.
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.