2. Residual food particulates and or mouth prints around the "rim" of a glass after having been put through a dish washing cycle.
3. The accumulation of feces in the hair around the anus of a "Lap dog"
2. There was "rimcrust" on a glass I wanted to use because someone did not wash the glass before putting it into the dishwasher.
3. Don't let Sally's dog sit in your lap or you'll get brown rings from the "rimcrust" on it's butt.