What is the meaning of Catchword?

A word at the end of 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.)

A word or expression repeated until it becomes representative of a particular group or time; a slogan or buzzword.

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

A word printed (often in large or bold type) at the head of a page or other section of text, serving to draw a reader's attention or summarise contents, especially in a reference work; a heading.

Source: wiktionary.org