1. adjective Honest and open, without any attempt to hide emotions. Often used in the phrases "heart-to-heart conversation" and "heart-to-heart talk." I know you two don't see eye-to-eye, but if you really sat down and had a heart-to-heart talk, I think you'd realize you are both working toward the same goal.
2. noun An honest and open conversation, usually about a serious topic. Jim sat down with his son and had a heart-to-heart about the dangers of peer pressure and drug use.