烟消云散

vanish like smoke and disperse like clouds—completely vanish

♦ 她方才那一阵兴奋又~了。 Her high spirits of a moment ago suddenly passed away like a breath of wind.

♦ 他紧张的心情, 被我这一番笑谈, 一下子冲得~了。 At my friendly jesting, his tension melted away.