Kit up is an action word that implies putting on clothing or gear for a particular purpose, such as for sports, outdoor activities, or military operations. There are a variety of synonyms that could be used instead of "kit up" depending on the context. Some options might include phrases like gear up, suit up, prep up, clothe oneself, or equip oneself. Other potential synonyms could include phrases like arm oneself, dress for success, assemble one's equipment, or don one's uniform. Ultimately, the right synonym for "kit up" will depend on the situation and the specific context in which the action is taking place.