The term 'reference word' is a type of word that is used to refer to something else. It is often used in literature, poetry, and other forms of writing to refer to a person, place, or thing without actually naming it. For example, a writer might use the phrase 'the man in the hat' to refer to a character without actually naming them. Reference words can also be used to refer to a concept or idea, such as 'the great unknown' to refer to something mysterious or unknown.