"Cup size" typically refers to the measurement used to determine the size of a woman's bra. It represents the volume or depth of her breasts, with larger cup sizes indicating a larger bust size. Full definition
There are, of course, some fairly obvious reasons why a coffee chain might want to offer a larger cup size, starting with customer demand. (canadianbusiness.com)
This is a favourite amongst women with smaller boobs who get to enjoy the benefit of going up a couple of cup sizes in their pregnancy. (bounty.com)
I recommend for A to C cup sizes due to the fitted bust. (renttherunway.com)