Technically any
fold of fat of a morbidly obese person, but in common usage
one that harbors foul-smelling excretions. These can be
simple body odor, areas that were too hard to reach during showering, or areas that have become fouled through elimination, the impossibility of spreading the
cheeks, or constrained by the shape of a toilet seat (the latter two causing a "muddy fatcrack"). The word can also be used to describe odors caused by a fatcrack - in this case 'fatcrack' is most often experienced when the fat person moves, releasing a bolus of odor, or 'fatcrack'.
1. "Damn, that lady on the bus had some serious fatcrack going on."
2. "What's that smell? - Oh, that's
Ruth, she's got a
muddy fatcrack".