Person: "I want tile for the floor of the place in my house that has a bath in it. The place in my house with a bath in it is also a room used to take a bath. This place in my house with a bath in it which is also a room used to take a bath needs tile on the floor of it."
Waterproof smear left by an untidy toilet user(usually on a virgin train)which starts below the rim and inexplicably continues and survives intact beneath the waterline.