That toilet deposit that just won't flush but prefers to bask in the bathroom light floating on the surface.
Floaters have different levels according to the amount of flushes required to make them go down.
Some people give up and leave them for others to find.
It is 2nd only to an actual holy crap.
"Urgghhh who left a floater?"
The floater is almost impervious to toilet flushing.