radtabulous Share definition Flag (adjective) A combination of rad, fantastic, and fabulous. Expressing the pinnacle of that which is cool. The boy's guitar skills were so radtabulous, Brian May would crap his pants if he heard them! radtabulous by Peter Coleman November 4, 2004 0 0 Get merch Get the radtabulous mug. Buy Now — $32.95 See more merch