The part of the toilet between the tank of the toilet and the toilet bowl. This is where pubes, dried urine and all sorts of awfulness reside.
Much like an actual
taint the 'toilet taint' is merely the connection between two major features. While not particularly useful, it is extremely necessary.
Person 1: I have to throw out my toothbrush it fell on the toilet taint.
Person 1: I cleaned the bathroom!
Person 2: No you didn't! There is still a forest of pubes and 2 years worth of dried urine on the toilet taint!