1. a memorable or effective word or phrase that is repeated so often that it becomes a slogan, as in a political campaign or in advertising a product.
2. Also called headword, guide word. a word printed at the top of a page in a dictionary or other reference book to indicate the first or last entry or article on that page. Compare running head.
3. a device, used especially in old books, to assist the binder in assembling signatures by inserting at the foot of each page the first word of the following page.
4. keyword (def 3).
Origin: 1720-30; catch + word
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