noun
one of a series of rounded notches in the fore edge of a book to indicate sections
• Hypernyms: ↑notch
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noun, pl ⋯ -dexes [count]
: a series of small cuts in the edge of the pages in a large book that are labeled and that make it easier to open the book to a particular section
a dictionary that has a thumb index
thumb-indexed adj
a thumb-indexed dictionary
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a series of cuts in the edge of a book, with letters of the alphabet on them, to help you to find the section that you want more easily
Useful english dictionary. 2012.