A fat substitute used to make Potato Chips fat free. Like those oh so delicous fat free Pringles. Ok it can be used in other things than potato chips, but they are its most common usage.

Supposedly eating it can have some side effects like the runs.

Olean® is the brand name for the chemical Olestra.

Apparently, some of the early implementations of Olean were especially viscious and had to be thickened up to make the product less expeditious, and to reduce the occurence of anal leakage.