a term, much like "bitchassness," used to describe individuals or acts that are shady, back-stabbing and/or dishonest; can also be used to describe acts of questionable fidelity, such as 'creepin'' with your friend's girl
"Did you see Darius chillin' wit Chinika the other day?"
"Yeah, bruh, that's fucked up. Chinika is Darrell's girl."
"See, bruh, that's the kinda fuckassery I can't stand!"
2. To be beaten badly at a game or sport, resulting in the feeling of being fucked in the ass
3. When someone (or someones) really gets on your nerves, in a manner simmilar in emotion and sensation to being fucked in the ass
1. Fuckassein curb check!
2. Matt Ryan was creamed all day by the Giants fuckassein defensive front.
3. I had to stand there and listen to those fuckassein customers ask me about the fuckassein buffalo wings. There is a goddamn sign in front of your fuckassein face you dipshit.