Brainpan, also known as cranium, refers to the bony structure that protects the brain. Interestingly, there are not many antonyms for the word brainpan. However, one antonym could be "mindless," which suggests a complete lack of intellectual ability or mental activity. Another antonym could be "stupid" or "ignorant," which refers to a lack of knowledge or inability to comprehend complex ideas. Lastly, "unintellectual," "uneducated," or "uninformed" could also serve as antonyms for brainpan, as they describe individuals who lack intellectual curiosity or are lacking intelligence. Regardless of the antonym used, "brainpan" is a term seldom used in everyday language.