(adj.) A person, place, thing, or idea that is just so incredibly awesome that no other word can describe it. Derived from the words spiffy and fantastic, it has been steadily catching on with teenagers nowadays (as steady as a snail in a molasses swamp, unfortunately). Tends to be used more by females than males, interestingly enough.
Person A: "Dude, I finally thought up a word to add to urbandictionary.com!"