The antonyms for the term "brush up" include words like neglect, abandon, ignore, disregard, forget, and overlook. These words imply a lack of interest or effort in improving one's skills or knowledge. If someone neglects or abandons a task, they are not attempting to improve it in any way. Ignoring or disregarding a subject means that one is not paying attention to it, and forgetting it means that it has been completely erased from one's memory. Overlooking something means that it is not given the attention that it deserves, resulting in no improvement. All of these antonyms are the opposite of "brush up," which means to improve upon something or polish one's skills.