A crusty, rancid, solid or semi-solid deposit left usually on the front rim of a toilet seat. This is usually caused by a person who does not properly or adequately wash the space between their genitalia and anus (i.e. "taint") and, hence, the residue from said area is smeared across the seat and incubated (or "caked") onto the seat so badly that usually a vigorous scrubbing is needed to remove the viscous substance.
"Holy freaking God, Chris needs to wash his under-carriage. Just look at that taint cake he left on the seat."
by Crashmanshibby March 24, 2007