(1):

(n.) A word or phrase caught up and repeated for effect; as, the catchword of a political party, etc.

(2):

(n.) The first word of any page of a book after the first, inserted at the right hand bottom corner of the preceding page for the assistance of the reader. It is seldom used in modern printing.

(3):

(n.) Among theatrical performers, the last word of the preceding speaker, which reminds one that he is to speak next; cue.