The term "brush upon" typically means to review or touch briefly on a subject. However, when seeking an antonym for this phrase, we can consider the opposite meaning of neglect or disregard. Other possible antonyms could include deep dive, fully explore, extensively research or in-depth study, which all entail a greater level of attention and dedication to learning about a topic. Similarly, some antonyms for "brush upon" could include overlook, ignore, or pass over, which indicate a lack of interest or attention to a particular subject. Regardless of the antonym, it is important to approach learning with an open mind and willingness to fully engage with the material.