bun
noun uk/bʌn/ us/bʌn/
(FOOD)
B2 [ C ]小圆面包;小圆甜蛋糕
a small, sweet, usually round cake
a cinnamon bun 桂皮味小圆面包
B2 [ C ] mainly US（水平切开的）小圆面包;（尤指）汉堡坯
a small, round piece of bread, especially one that is cut horizontally and holds a burger
a hamburger bun 一个用来做汉堡的圆面包
(HAIRSTYLE)
[ C ]圆发髻
a woman's hairstyle where the hair is brought together into a round shape at the back of the head
She wore her hair in a bun. 她将头发挽成一个圆发髻。
(BOTTOM)
[ C usually plural ] mainly US informal屁股（的一边）
a buttock (= one side of a person's bottom)
Idiom
have a bun in the ovenidiom old-fashioned humorous 怀孕
to be pregnant