The term "vault up" is often used in the context of jumping, climbing, or scaling up a high object or barrier. Antonyms for vault up could include phrases like "descend down," "move backwards," or "slip down." Other antonyms might include "stay grounded," "move laterally," or "remain at a low level." These opposites of vault up could relate to activities like walking, crawling, or staying close to the ground. In general, antonyms for vault up suggest actions that are opposite or contrary to jumping, ascending, or scaling up a high object or barrier.