A middle aged man, who is overweight and out of shape, who won't shut up talking about what an athlete he was in high school.
Walter: "Erez, your just jealous because I ran the 100 meter dash in 10 seconds flat, was an all american wide receiver and got all the chicks"
Erez: "Dude, bullshit! You're just a fatlete!"
A person who claims to be an athlete, but is in fact covered with a dubious layer of fat rather than the muscle you'd expect them to have.
'Why is he so chubby..? I thought we were watching the Olympics, not the Teletubbies!'
'...Should have gone to SpecSavers mate. He's just a fatlete, that's all.'
Having the physical traits of enlarged body part (mainly the gut region.) Most fatleens swim with a t-shirt on to keep their tits from floating to the surface. Similar to a walrus or elephant.
"Where is that lard-ass fatleens at?" said Mike. "Probably closing down our local buffet" replied Tom.