屁股

buttocks / bottom / butt / back part

fart / flatulence / nonsense / (usu. in the negative) what / (not) a damn thing

thigh / part of a whole / portion of a sum / (stock) share / strand of a thread / low-level administrative unit, translated as "section" or "department" etc, ranked below 科[ke1] / classifier for long winding things like ropes, rivers etc / classifier for smoke, smells etc: thread, puff, whiff / classifier for bands of people, gangs etc / classifier for sudden forceful actions

to wipe one’s ass / (fig.) (coll.) to clean up sb else's mess

lit. the butt governs the head (idiom) / fig. where one stands depends on where one sits / one's views are shaped by one's circumstances

anus

butt cheek / rump

(dialect) a fall on the buttocks / pratfall

to spank sb's bottom

to make oneself scarce / to slip away / to take French leave

cigarette butt

to show warm feelings but meet with cold rebuke (idiom) / to be snubbed despite showing good intentions

to have overslept / Rise and shine!