catch·word / ˈkachˌwərd; ˈkech-/ • n. 1. a briefly popular or fashionable word or phrase used to encapsulate a particular concept: “motivation” is a great catchword.2. a word printed or placed so as to attract attention. ∎  chiefly hist. Printing the first word of a page given at the foot of the previous one.

CATCHWORD.
1. A memorable word or phrase, repeated by many people.

2. Also headword, guideword, flagword, running head. A word printed at the top of the page of a work of reference to indicate the first or last entry or article on a page; part of a series of such words intended to help users find what they want.

3. Also KEYWORD. In library science, a memorable or important term in the title, text, or abstract of an item being indexed and that is therefore used in the index entry.