The term "tuneup" refers to the process of improving the performance of an engine, machine, or other system. Antonyms for tuneup include neglect, disregard, and indifference. When a system is neglected, it is not maintained or given the necessary updates to keep it running smoothly. Disregard implies a lack of concern or care for the system's performance. Indifference, on the other hand, suggests apathy or unconcern about the system's welfare. Other antonyms for tuneup include sabotage, damage, and breakage, all of which can result in a breakdown or failure of the system. To avoid such outcomes, regular tuneups and maintenance are necessary.