1.) The dead skin yielded under your fingernails after scratching your buttocks.
2.) To scratch your posterior.
To skinass too hard or too often would be ill-advised, as you may end up developing poop finger
Shaun headed to the nearest restroom after noticing he had a case of skinass on his hands.
Jordan always skinasses right when he gets out of bed in the morning. He may be developing a rash.