To chew the fat or chew the rag means to chat in a leisurely and prolonged way.

For example:

I’m going to meet up with my friend and chew the fat for a while.

Don’t just chew the fat all day; we have work to do!

They met up once a year to chew the fat about the old days.

Tradução:

Bater papo, jogar conversa fora, conversar fiado, fofocar.