'She thinks that he has a really heavy groove.' What does groove mean here?

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I think the way he behaves .
Maybe the more talkative.

Answer

It's hard to say without more context, but in this case I think "groove" means the way he behaves, and his attitude towards things. The word "heavy" can be used as a slang word meaning "serious and sad". A person with a "heavy groove" would be a person who rarely smiles, and who is always thinking about serious things.