Abbreviated from "there's a rhinoceros in the room," this is an attribute (a storey element or of the author's writing) which is shriekingly obvious to everyone except the people closest to it. (In horror movies, the idiotic willingness of characters to split up and search dark mansions is a rhinoceros.) The term is most useful in a critiquing context as a means of helping an author identify recurring tropes, tics, or fetishes in his own writing.