noun
protruding buttocks; big butt
Colloquial and slightly vulgar term for buttocks that stick out prominently.
あの子は出っ尻で、ジーンズがよく似合う。
That girl has a big butt and looks great in jeans.
彼は出っ尻を気にして、スカートを履かない。
She's self-conscious about her protruding buttocks and doesn't wear skirts.