A person most widely known for the fat that forms mainly around their ass as a result of the ingestion of McDonalds
While found in other countries, the McFatAss tends to breed most successfully in America. They are most comfortable in packs of 3 or 4. However, their shitty 1991 Honda Civics don't usually allow the easy transportation of these packs. Their natural enemy is the scale, stair-masters, gyms, P.E. teachers, movie theatre seats, airline seats, single servings, and anything healthy.
In their natural habit, (a McDonalds of course)they can be very easy going and possibly friendly.
DON'T BE FOOLED! For as soon as the McFatAss is out of its comfort zone, it will attack! The most common form of attack has been biting!
The McFatAss is usually not born fat. It usually develops a sweet tooth for fast food later in life. However, if two McFatAss mates (usually unsuccsessful because one of the two will either have a heart attack, or be crushed to death by the other)they will create a McFatAss baby! The McFatAss baby is very cute when first born. However, that cuteness will soon turn into an ugly McFatAss.
There were a few rare occasions where I actually saw 2 McFatAss females prostituting themselves in front of a McDonald'd Drive-Thru