The phrase "a flat chest" is correct and usable in written English.
It can be used in contexts discussing body types, fashion, or health-related topics.
Example: "She wore a dress that accentuated her figure, but she felt self-conscious about having a flat chest."
Alternatives: "a small bust" or "a slender chest".
Unless you are tall, with a flat chest, these dresses make you look six months pregnant, hanging straight down from your breasts to form an unflattering tent.
"There were nights when I'd see Chris coming to bed wearing boxer shorts and with a flat chest, and I'd just cry.
When I looked down, what I saw turned out to be just a flat chest with fresh scars on their way to looking healed.
"If she was going to do role playing of what she would be like when she was 16 or 17, it was a little stupid to play with a doll that had a flat chest.
What Amanda remembered was glasses, a flat chest, hand-me-down bobbled jumpers (Amanda had refused to wear hers, once the wool went like that), a reputation for good marks at the school where she had a scholarship (not the school that Amanda paid for), and a stubborn, sulking resistance to Amanda, who — used to capitulation — had been intrigued.
She had a small frame, a flat chest, sleek hair and a "kooky" face.
A binder of the kind made for trans men is even better, but comes with some health risks and can be a pretty drastic step if you don't want a completely flat chest.
Born female, Christie Elan-Cane, 36, appears somewhere further along the gender continuum than Zoltar, with a shaved head, flat chest and khaki shirt.
Watching a man's flat chest grow into two small mounds before my eyes is incredibly strange and disconcerting.
I was 19 and had finally finished healing from my top surgery, a double mastectomy removing both of my breasts and leaving me with a masculine and flat chest.
If you have a small or flat chest, you're in luck.
