Goredragons, or rather their feces, are mentioned only once in How to Seize a Dragon's Jewel, as part of the supplemental pages on how to speak Dragonese.

"Toothless mak ta me m-m-ost speshally griefspotties. Toothless's runners pop in a cack-cack di Goredragon, plus me pressit muchwide ondi floorsheet.
I make you my most heartfelt apologies. I seem to have stepped in Goredragon poo and trodden it all over your carpet.

There is no description or information of any kind on this once-mentioned dragon. It is possible that the author may have been thinking of the Goreslingus Rex (also only mentioned once) seen in "The Complete Book of Dragons", or vice-versa. The Gorebluffer is also possible.