to be absolutely ON ONE. Just generally trippin', tweakin' out, jacked up, or crazy. Not necessarily due to drugs.
Could also mean on the right amount of drugs and alcohol to be on a whole new social level of whacked out.
Or a legit crazy person.
“You see Dukes rip his shirt apart on the dance floor when 0 to 100 came on last night? Homeboy was certified.”
"Wow. Jessica getting jealous of Nick and Sarah when she's not even hooking up with him. Certified."
Certified is a street gang created by Lp certifiedbased in Durham, North Carolina. But quickly spread to the west coast and is currently world wide. They have been moving under the radar in silence since 2003 but off and on over years been exposing there true nature to public eye.