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!"
The process of inserting the penis in to the anal hole
Jenna and Mike had great time engaging in fuckassery.