catch·word 
(kăchwûrd′, kĕch-)
(kăchwûrd′, kĕch-)n.
1. A well-known word or phrase, especially one that exemplifies a notion, class, or quality: "We're turned off by the label 'sexy' when used as a catchword for every new design" (Miriam Lang).
2. Printing
a. A guideword.
b. The first word of a page printed in the bottom right-hand corner of the preceding page.