Catchword
Part of speech: noun
Definition: A word under the right-hand side of the last line on a book page that repeats the first word on the following page. A word or expression repeated until it becomes representative of a party, school, business, or point of view.
Guideword
Part of speech: noun
Definition: A watchword; a word or phrase that serves as one's guideA word that is printed at the top or bottom of the page in a reference work, in order to help readers find a specific entryAny of the words in a memo or email that define metadata regarding the message, such as sender, recipient, and subject