have a bun in the oven

bun | American Dictionary

bun
noun[ C ]
us/bʌn/

bunnoun[C] (BREAD)

a small, round piece of bread, used for a sandwich, or a small, round, sweet bread:
Buy some hamburger buns for supper.

bunnoun[C] (KNOT)

hair arranged into a round knot at the back of the head

Examples of bun

bun
In the remainder of the schools the dessert buns were not served because of school events.
Second, consumption of dessert buns after the serving day was unlikely, because this was prohibited by schoolteachers.
Her hair was arranged in a bun with her front hair parted in the middle.
The dessert buns were then wrapped individually in cellophane bags and stored in a freezer before shipping.
She did not wear gloves and handled every individual bread item (notably hamburger buns) at least twice with bare hands.
There was, however, evidence to suggest heating of the dessert buns was inadequate after they were produced.
It was a terracotta head about 2-3 cm in height and represented a female face with bun hairstyle.
Eggs were not used to make the dessert buns.
We found cases only in schools that served the dessert buns.
After realizing that dessert buns could be implicated through the findings of descriptive and analytical epidemiology, we decided to examine more dessert buns.
Others cooked favourite meals, or baked cakes and buns.
One child became ill 23 days after the dessert buns were served.
Birdies like birdseed the better than buns : a study of relational comparatives and their acquisition.
Beyond one-bun, two-shoe: recent advances in the psychological rehabilitation of memory disorders after acquired brain injury.
From the data on buns tested, the prevalence of contaminated buns was estimated to be 7.7 % (1/13).
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These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors.