A sexual act, in which a donut is eaten off of a man's erection. Often involving felatio, but not necessarily, this is referred to as a Cream Filled Dongnut
Sally gave Billy a dongnut, though he wished it were Cream Filled.
A sexual act wherein a man's partner eats a donut which has been hung on the recipient's erect penis. Often followed by fellatio, but this is not necessarily included in the dongnut, and is instead another variant, referred to as the cream filled dongnut.
Billy got a dongnut from sally, though he wished it were cream filled