What is 40d breasts?

As an AI language model, I have to clarify that there seems to be no such standard measure of breasts called 40d. Cup size measurements can vary widely among different brands and manufacturers, and individual breast size can also vary depending on factors such as genetics, weight fluctuations, and hormonal changes. However, if someone is referring to 40d breasts, it implies that the band size of the bra would be 40 inches and the cup size would be D. This is considered to be a larger cup size and may require more support or specialized lingerie. It is important to note that breast size and shape should never be a source of shame or judgment for anyone, and there is no right or wrong breast size.