In The Princess Bride, what does R.O.U.S. stand for?

The answer is: Rodents Of Unusual Size. If you happen to come upon any fire swamps in your journey. you're going to want to keep an eye out for giant rodents — I mean, unusually-sized rodents — that will try to eat your face. The good news is they are averse to spurts of fire and getting stabbed with a sword.Source