look up any word, like the eiffel tower:
 
1.
What the drive-thru cashier must smoke in order to suggest super-sizing your meal 5000 times a shift,25000 times a week, millions of times a year,billions and billions served.
"Welcome to Mcdonald's. Can I take your order? **snort**"
My mother-in-law and I gave each other a knowing look. The loudspeaker snort was a dead give-away for Mcfatty inhalation. We bummed a couple of tokes in order to keep quiet, and then headed to the motel with our post-coital snack.
by pantaloon January 24, 2008
 
2.
1) A person who is moderately to morbidly obese from eating mass quantities of McDonalds food. Usually an American.

2) My middle school religion teacher, Ms. Miles
(Please don't give a thumbs down because of this definition. The one above is the real one.)
Ms. Miles.

Look at that blob waddling down the street. That lady, Ms. Miles, must be a Mcfatty.

Look at Ms. Miles, my middle school religion teacher, stuff her face with that Big Mac. She is a Mcfatty.

Since look at all those tools, including Ms. Miles, standing in line in Mcdonalds. They are all Mcfatties.

The Mcfatty devoured 3 Big Macs and a large fry in one sitting. Her name is Ms. Miles.

When the Mcfatty, Ms. Miles, walked down the hall, I yelled "Earthquake" because she was so morbidly obese the building shook as she walked.

I yelled "Look out!" as the Mcfatty, named Ms. Miles, slowing jiggled towards Will. He would have been trampled and crushed to a gruesome death if I didn't admonish him of the corpulent whale approaching.
 
3.
slang for the evil corporation usually called McDonald's, due to the high amount of fat in the food served there.
Todd: "Hey, wanna go to McFatty's??"
Jena: "Nah... I'm on a diet"
by Teh Franilow April 17, 2009
 
4.
someone who has become so fat that they cant accomplish simple tasks

one who gets a work out from climbing stairs
that dude is such a McFatty
by jason1228 December 06, 2009
 
5.
1.)Anyone in the Prince of Tennis fandom.

2.)Fangirls

3.)Yaoi Fangirls

4.)BNF's

5.)Anyone who ships fictional characters together.
Bobbissimo is a Mc Fatty, who has jiggy arms.

Prince of Tennis fangirls are all Mc Fatty's.

by bookshop July 13, 2007
 
6.
The unusually large people that sometimes work in fast food.
Dang, that Mcfatty needs to lay off the fries.
by bajabeetle March 23, 2007
 
7.
An awesome MCconcoction that consists of a MCchicken piled onto a double cheeseburger with bbq sauce added.
Me: "The Mcfatty sounds like the grossest idea since the roman helmet."
n00b: "GOD I love mcfatties!"
by NicholasridiculouS November 15, 2005