Verb. To procrastinate or find unimportant activities with the purpose to simply annoy people for your own pleasure. Such activities include; aimlessly wondering around in someone's office, blablabla-ing with friends online while munching on food for the purpose of munching or otherwise focusing on being an nuisance.
Q: Honey why are you walking around in my office with a piece of KFC stuck in your mouth while blablabla-ing with your friends?
When people (especially cops) stand around not doing their jobs but instead eating food and/or drinking coffee.
Joe: Wow, this traffic is really backed up. You'd think the cop would be directing all the cars.
Billy: No, he's too busy fatassing. Look he's got a donut in one hand and a coffee in the other!
Term used to define eating a large quantity of food during one meal or at a fast food joint/restaurant/buffet. It may even be used for when you're at home! Originally excavated by the Straight Up Squad.
Kevin and Luis are Fatassing It Up at Jerry's by eating two large pizzas.