Best definition
yawn pong
The irresistible and unfightable urge to yawn when someone yawns first at you.

Our bordem at dinner got so bad that a yawn pong match broke out. Service!
yawn pong: define #2
yawn pong
A game played by tired people. In short, one person yawns and then the other person does. Should the original yawner yawn twice before the second person yawns once, player one has one point.
We played tweleve rounds of yawn pong last night.
yawn pong: define #3
yawn pong
The foul smelling woft of bad breath that you expell first thing in the morning when yawning usually after a night out drinking and smoking having collapsed on your bed forgetting to brush your teef.
I woke up after a heavy nights boozing next to a girl i did not recognise with a traffic cone in the corner of my room and a bike lock round my neck. She yawned and jeeeezus did i get the full force of her yawn pong. I then threw up on her.