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To become serious, somber, or emotional. Wow, I didn't mean for this meeting to get heavy. Anybody got any jokes to lighten the mood?
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
get ˈheavy(informal) become very serious, because strong feelings are involved: They started shouting at me and it soon got very heavy.
Farlex Partner Idioms Dictionary © Farlex 2017