The one-word form of the phrase "Son of a bitch", commonly used by rednecks. Also spelled "Sonnuvabitch", "Sunnovabitch" and "Sonnovabitch", all present the same insult. Although mainly used by rednecks, it can be used by anyone, but it would sound weird.
"Hey Tom, that sunnuvabitch just tried to steal gas!"
"Bro, that sunnovabitch took my character out again in Halo 4!"
"Sunnovabitch I'ma slap you real hard if you don't shut the f*ck up"
bitch son of a bitch