Verb-Performing sexual intercourse through the anal cavity.
Adjective/Adverb-describing something in a good, or bad, sense, usually when either excited or upset.
Accidental-When your interrupted in a conversation, and you attempt to go back to what you where saying by starting your sentence with, "But..." then you accidently say, "Fuckin..."
Adjective-"Oh man, that class was butt-fuckin." or "Dude, the homework is butt-fuckin hard..."
Adverb-"He runs butt-fuckin fast"
you, "Oh man the other day I was with Sarah..."
friend, "Oh did you hear she got the clap?"
you, "Oh no way? Go figure... but, fuckin she wouldn't stop talking about her boyfriend, it was pissing me off."