An intimate sexual position consisting of one male protruding another males anal canal with his penis.
It gets it's name from Vatican City, in which women are not permitted, hence if any intercourse is to go on inside the Vatican, it must be man in man.
The "donut" part of the term comes from the anal canals shape which resembles somewhat of a sweet bakery treat, ie a donut.
AKA "dirty gay bumsex"
I heard Bob and Fred love their Vatican Donuts!