adj-term used to define any behavior, look, person, activity, outfit, food, car basically ANYTHING that is weird, out of the ordinary, completely ridiculous, or just down right wrong.
also can be a way to let friends know you are hammered.
"I can't believe you made out with a gay guy wearing a banana suit last night, you were so billis."
"the person driving that car is being so billis right now, they just cut me off."
"i just took mad shots, i am so billis."