It's random when you would be hit that instead you are not. This is primarily useful on defense, where enemy combos will randomly not connect, allowing your defender to block and counter, as well as giving haste, one of the best buffs in the game. While not in the top five defenders, as bronze start lowers her base stats and some multihits have enough hitstun to connect even with a miss, between having one of the best combo interrupting passives in the game and one of the best condition defenses in the game, Just Kitten is a stellar option for defense, especially on a budget.