Longman Dictionary English From Longman Dictionary of Contemporary EnglishRelated topics: Newspapers, printing, publishingthumb indexˈthumb ˌindex noun [countable] TCNa line of round cuts in the edge of a large book which have the letters of the alphabet on them and help you find the part of the book you wantExamples from the Corpusthumb index• Do I have a thumb index? ldoceonline.com
