Sonicboom is the name of a powerful dual attack by Robin and Cyborg, capable of defeating large enemies (Cinderblock, Plasmus) in one hit. It consists of one of Robin's explosive discs and Cyborg's sonic cannon blast. The attack begins with Robin and Cyborg running along opposite walls in a room. Robin throws his explosive disc while Cyborg fires his sonic cannon, triggering the explosive disc and causing a massive explosion.
The attack was only seen in the episode Divide and Conquer, where it first failed against Cinderblock (due to them getting their legs tangled). It was later successful against Plasmus.