The word "undergone" means to have experienced or undergone a certain process. Some antonyms for "undergone" could be "avoided," "evaded," or "bypassed," indicating that the process was not experienced or endured. "Ignored," "neglected," or "overlooked" could also be antonyms, suggesting that the process was not given proper attention or consideration. Other antonyms might include "skipped," "canceled," or "dropped," indicating that the process was intentionally avoided or halted. Ultimately, the appropriate antonym for "undergone" depends on the specific situation and context in which it is used.