[Ir. oll, great; péist, fabulous beast, reptile, monster].
Dragon-like monster from Irish oral tradition. In the best-known story, the oilliphéist cuts the route of the Shannon River when it hears that St Patrick has come to drive out its kind. In a comic addition to the story, the oilliphéist swallows a drunken piper named Ó Ruairc [O'Rourke] who continues to play inside the monster, thus annoying it until coughed up and spat out. ScG counterpart: uilepheist. See also CAORÁNACH; MUIRDRIS; SÍNACH.