Skidmarks are brown streaks left on the porcelain bowl of a toilet when someone takes a big firm dump that rubs the porcelain bowl swirling around until it orients itself for exit down the pipes.
Multiple skid marks seen on the pavement in movies that predict the car chase is about to get exciting. Usually left by the stunt driver doing practice runs.
Nearly half of the chase scenes in French Connection are littered with psychic skidmarks. But you have to look fast, These scenes usually last 1 to 2 seconds.
When soft, still plyable anal dischanrges rub so close to the offenders' undergarments that a fecal stain is left behind. May also occur when the issue is "forced." I.E. Butt picking, massaging of anal irritations, or sloppy wiping techniques. See also "streaks."
Dammit Donnie, the line for the port-o-let was so long I had to rush my post crap rectal cleansingtechniques. Now I have smelly 7-1/4 inch skidmarks as a result!