Much like the fucked up things in the movie "The Hills Have Eyes". But the person is just fucking insane without any nuclear remains around to mess them up. They are just retarded and crazy from the get go.
Really...a psychobilly can be anyone just crazily pissed off or just any freak ass person you see. Someone thats actions or looks can be related to in anyway to the things in "The Hills Have Eyes".
"Man did you see that fucking psychobilly bitch scramblin down the street!?"
"Man my goddamn step-mom is a psychobilly...she just came in the house screaming like a fucking retard without its pills."