bun

bun /ˈbʌn/ noun
plural buns
bun
/ˈbʌn/
noun
plural buns
Britannica Dictionary definition of BUN
1 
[count] : a small, round or long bread for one person to eat
2 
[count] : a small, usually round sweet cake — see also sticky bun
3 
[count] : a way of arranging long hair by twisting it into a round shape at the sides or back of the head
4 
buns [plural] US, informal : the two soft parts of the body that you sit on : buttocks

have a bun in the oven

informal
: to be pregnant