The opposite of Rad. Uncool, disappointing, bad.
"I friended her on Facebook and it turns out she had a boyfriend, it was the anti-rad."
Person One "Last night dude spilled his beer on me and then puked on my carpet!"
Person Two "That's the anti rad dude."
Person One "He volcano'd the bowl then said he would chip in a few bucks to pack another!"
Person Two "That dude is the anti rad, I'll avoid smoking him up at all costs!"