A simple fusion of Scum and Believable. Used to describe (traditionally female) people who are deemed to behave or present themselves in a manner which is considered slutty.
a) My god, what IS she wearing?
Looks pretty scumbelievable to me.
b) Did you hear about last night?
Yeah i know, that one is pretty scumbelievable if you ask me.
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.