In the fashion world, it means to make something better, generally by tweaking or quirking it to better fit what it's supposed to do both functionally and artistically. It's become most popular due to its frequent use on the hit Bravo show Queer Eye for the Straight Guy, usually by their fashion guru Carson Kressly. It is very hard to pronounce, and even harder to spell, many times often misspelled 'jujj' or 'jooj'. Pronounced "zhuj", by the way.
Carson: "Just tszuj it a little, and you're set!"