ButtWater is when you have really bad diarrhea...
That when you go to the bathroom and pull your pants down you instantly start pissing out shiting profusely Intel your done
Dude last night after eating taco bell i got instant buttwater
Vulcanic Butt Water is an activity where water or some kind of liquid (beer is the most common) ir poored trough ones back, passes trough the butt crack and ends up in the other person face. The first mentions of this activity appeared in Budapest-Hungary at a party hostel called Grandio Party Hostel by a group of Portuguese individuals in a bachelor party called "Bizeus Bachelor Party"
That guy is sleeping at the couch, let's vulcanic butt water him.
The local wings place is giving out buffalo water butt, free of charge. You'll be peeing out of your ass so many times the salmonella will be hanging on like a palm leaf in a fucking hurricane.