verb (used with object)
to provide (a book) with a thumb index.
a series of labeled notches cut along the fore edge of a book, to indicate the divisions or sections.
Origin of thumb index
First recorded in 1900–05
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a series of indentations cut into the fore edge of a book to facilitate quick reference
(tr) to furnish with a thumb index
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012