windsmear (noun)
- Fecal staining produced by a violent passage of wind.

Windsmears are produced when airborne particals of feces (or "winnit dust") becomes trapped within cloth, usually underwear but frequently bedsheets.
A windsmear is marked by its resemblance to, say, the spray of an aerosol. They are usually dry to the touch.

Not to be confused with skidmarks.

When you eat dirt for the first time and leave your family to build a shack in the woods