backside
n. 背部；后方；臀部
复数 backsides
例句
The lad fell backwards, landing on his backside.
那个男孩向后倒下去，屁股着地。。
《柯林斯英汉双解大词典》
He gave the donkey a mighty prod in the backside.
他在驴的屁股上狠狠地捅了一下。
You'll get a smack on your backside if you're not careful.
要是不小心，就打你的屁股。
《牛津词典》
