Bitch, bastard, and/or retard, all rolled into one. Used as a term of endearment between friends. Could commonly be heard after one of a group of friends does something stupid, or could be heard after a long night out of drinking.
Jon: Dude, did you just try to fuckin' hit on Heather?
Chris: Yeah man, liquid courage, all I gotta say!
Brian: What a friggen Bichasto!