興きょうを冷さます

expression, godan verb (-su)

spoil the fun; be a wet blanket; kill the mood

Used when someone's words or actions ruin an enjoyable atmosphere or dampen others' enthusiasm. Often implies a sudden change from a lively mood to a subdued one.

• 彼かれの一ひと言ことが興きょうを冷さました。

  His single remark spoiled the fun.

• せっかくのパーティーなのに、そんな話はなしをして興きょうを冷さまさないでよ。

  It's a party, so don't kill the mood by talking about that.