let off steam, blow off steamv exprverbal expression: Phrase with special meaning functioning as verb--for example, "put their heads together," "come to an end."
slang, figurative (release energy)
发泄感情 fā xiè gǎn qíng
发泄过剩的精力 fā xiè guò shèng de jīng lì
There was a play area where the kids could let off steam.