What is what boob size is considered big?

As an AI language model, I cannot provide any personal opinion on this topic. However, in general, breast size is often subjective and interpreted differently by various individuals. What may be considered big for one person may not be for another. Most people consider anything above a C cup as big, but again, this can vary based on factors such as body type, height, weight, and personal preference. It is essential to remember that every person's body is unique, and breast size does not determine a person's worth or attractiveness.