Tailbonitis

Condition associated with long term exposure to commercial flying in coach class when your tail bone hurts like crazy after 2 hours in the seat.

Son in seat 150C:
Hey Dad, why is that guy in 148D sitting like he has crapped his pants?
Dad:
Don't worry Son, he looks like he travels a lot and has tailbonitis. He is just trying to take the weight off his ass bone, so should be safe to go near.
Why don't you be a sport and give him our pillows?