backside

Those who are cute have a hateful backside.

If you tumble here, your backside will be squashed.

My backside is becoming flat from sitting for too long.

Tom slipped on the wet grass and fell on his backside.

deTom rutschte auf dem nassen Gras aus und fiel auf den Hintern. — Pfirsichbaeumchen

Spending all day at my computer is making my backside flat.