The antonyms for the word "bustiest" include "slimmest," "skinniest," "thinnest," and "leanest." These words refer to a person who is thin and petite, rather than having a well-endowed bust. Other possible antonyms for "bustiest" could include "flat-chested," "undeveloped," or "small-breasted." It's important to remember that these words are not necessarily negative, and that there is no "ideal" body type. Rather, everyone's body is unique and should be celebrated for its own individual qualities. Whether you're busty, slim, or somewhere in between, self-love and body positivity should always be your top priority.