Common insult like "dick" and such. Can be used to describe Justin Beiber and other people you don't like.
arsemasti (plural) (phonetically: arse-marst-eye)
Teacher: Why haven't you done the hand-written, 900 page essay I set for you yesterday you lazy fool?!
Me: I have dyslexia sir.
Teacher: That is no excuse you retard! (starts frothing at mouth)
Me: You're such an arsemaster!
Teacher: LAZY FUCKING DOUCHEBAG!
Teacher's boyfriend: You tell him Ben! *gropes arse*
Me: You guys are arsemasti.