A generalized reference to the use of one’s laundry tub as a toilet, usually the result of an urgent situation preventing one from making it to the toilet or the unfortunate result of having an unusable toilet. Taking a tub shit often occurs when one has limited time to defecate, such as when playing Warcraft and being given a short AFK.
Me: Where's Kirky? We need to pull.
You: He had to go. Don't worry, he's Tub Shitting so he will BB soon.