What is the meaning of Catchword?

A word under the right-hand side of the last line on a book page that repeats the first word from the following page. Such words served as aids to the bookbinder (to check rapidly for correct placement of leaves) and were also viewed by some readers as aids to smooth reading.

The last word of a speech, serving as a cue for the next speaker.

A word or expression repeated until it becomes representative of a party, school, business, or point of view.