1. To express, narrate, or reveal something to one. He loves telling imaginative stories to his grandkids. I wish I didn't have to tell this to you, but I'm flunking out of college.

2. To explain something to one who is unlikely to be unsympathetic to or negatively impacted by what one believes. Used as a sarcastic, pithy retort. A: "I don't think they should have given you a ticket. The sign is really unclear about when you can and can't park there." B: "Yeah, tell that to the judge." A: "Everyone on the planet should give up meat." B: "Tell that to the farmers who have built their lives around raising livestock."