An overweight, mouth-breathing complainer who blames his/her weight problems on everything other than what likely is the true cause, which basically amounts to eating too much and sitting on their fat lazy asses all day.
Rodney: "Damn, look at dude goin' downtown on that triple whopper!..... WTF is up with the diet Coke though?""
Chris: "Meh, I see that shit everyday, typical fatler behavior.".
A chubby, overweight or obese person. We all know a Fatler.
Elliot is such a Fatler!
Oh my god, he used to be well built, he's such a fatler now!
Look at the chins on that Fatler!