An extremely obese woman with nipples at least 12" in diameter that are visible through her clothes.
"Aw man, did you see our new substitute teacher? That chick needs to lay off the cheeseburgers and jog her ass around the block a few times."
"Yeah, and wear a thicker shirt! You could totally see her nipples, they were like freakin' deflated basketballs!"
"Now that's a nippopotamus right there."