Someone or something that is VERY cool and worthy of praise. Can also be shortened to "rack". Scooby snacks are-like-totally rad, so this is an easier way to say it that describes other totally rad things.
Admirer #1: Yo, that lambo is pretty rooby rack.
Admirer #2: Dat booty be pretty rack, yo.
Admirer #3: Dang, homie. That's a true rooby rack right there.
Man: What the hell is all that junk doing in the front yard?Woman: the rootboy came again....
Man: Great... I just don't get WHY he keeps filling our yard with roots and rootbeer, this is just so f*cked up... it serves absolutely no purpose... sigh.. i'll get the broom.... and visit the cops again... why did we want live here again?