Doing something extremely stupid or reckless usually for the amusement of others or for the thrill of doing something daring. Often occurs as a result of peer pressure.
The expression originates from the urban myth(?) of someone dancing on the railroad tracks and paying for the foolish mistake with their life.
Dana: Look at Jimmy. He’s dancing on the rails again
Bill: What an idiot! He’ll get hurt if he doesn’t stop it!
Pretending to like someone when both of you know you hate each other. Social and Professional settings.
My boss tried to fire me and I put in my 2 weeks notice so I could cash out my vacation package before he had the chance. He said "Hey Brother, do you mind running an errand for me real quick"? I said "I am so sorry buddy, unfortunately my tires are all flat." We both knew I was lying because my car was parked out front. We were Dancing On Water