fatgun

A variant of the slang word "shotgun" (a situation in a group of people where one person declares that they will ride in the passenger seat while the other 3 squeeze in the back seats of the car.)

When you are fat, preferably obese, you basically get shotgun. It would be really difficult to squeeze 2 more people in the back of a small car alongside a really fat person.

"fatgun!"
"huh?"
"i'm the biggest guy among us so i'll sit in the front to save the rest of you guys space"
"oh, okay, that makes sense"