It sounds like a nice way to describe a cute picture of a child with a cute puppy...but it's actually when one gentleman is gnawing on the phallus of another gentleman. Generally they don't draw blood but it does happen from time to time.
Don, can I gnawwwww on your engorged phallus after you've finished that carafe of Creme de menth?
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi