The act of eating a lot more food than everyone else in the group, causing everyone to call that person fatass.
Little Jimmy had three bags of candy and a large soda at the movie theater, so everyone, including his parents called him a fatass.
10 years later, Little Jimmy entered a middle school hot dog eating contest. Little Jimmy gobbled up record high 676 weenies, shattering previous record of 325 set by Michael Moore and tied by Rosie O'Donnell. Everyone, including the president of hot dog eating contests, called Little Johnny a fatass.
Another 10 years later, Little Jimmy finally moved into his own apartment where no one could judge his eating habits. Little Jimmy ate 62 big macs to celebrate. Despite dying of a clogged anus the next morning, nobody was around to call Little Jimmy a fatass, so technically he was not a fatass.