Meaning of thumb index

thumb' in"dex

Pronunciation: [key]
  1. a series of labeled notches cut along the fore edge of a book, to indicate the divisions or sections.


Pronunciation: (thum'in"deks), [key]
— v.t.
  1. to provide (a book) with a thumb index.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.