1. To eat excessively over time to a point where one becomes overweight or obese; process in which one becomes a fatass.
2. To eat an excessive amount of unhealthy food at one given time.
1. "I totally fatassified myself by having donuts for each meal for the last 4 years."
2. "Dude, you're fatassifying yourself by eating all those pancake batter and maple syrup dipped sticks of butter."