To converse, or to chatter in informal fashion. In Great Britain chewing the rag originally (late nineteenth century) was a colloquial term for complaining or grumbling, although one source holds it was an army term for persisting in an argument. Another source reports that the rag in question was a piece of cloth used when soldiers ran out of tobacco. Chewing the fat, more common in America, may have meant chewing on salt pork or fatback when supplies were low. Today both are colloquial clichés that simply mean talking in a relaxed manner.