1.(adj)An adjective or adverb form of prep, used to describe someone who is preppy or a prep. Derived from fantastic, spastic and prep. Mostly used in circumstances when one changes from something at the opposite end of the social spectrum, perhaps goth or nerd has a total changeover. Can be used as a noun on occaision.
"I can't believe he started wearing Aero stuff! He really went preptastic!"
"These brown flipflops are kind of preptastic, but I love them anyway!"