Like a Blowjob, except that instead of engulfing the entire Penis the one giving the Blowjob mainly focuses on the Bellend.
Dave: "Holy shit dude, Georgia gave me one hell of a Belljob last night!"
Johnny: "What's a Belljob man?"
Dave: "It's like a Blowjob but just on the Bellend! It was mad, I cummed like crazy!"
Johnny: "Ohhh shit dude! Niiiiice!"