noun Date: circa 1928 either of the terms at the head of a page of an alphabetical reference work (as a dictionary) indicating the alphabetically first and last words on the page
GUIDE WORD
Meaning of GUIDE WORD in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012