thumb index

¹ American  

noun

1. a series of labeled notches cut along the fore edge of a book, to indicate the divisions or sections.

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thumb-index ² American  

[thuhm-in-deks] / ˈθʌmˌɪn dɛks /

verb (used with object)

1. to provide (a book) with a thumb index.

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thumb index British  

noun

1. a series of indentations cut into the fore edge of a book to facilitate quick reference

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verb

1. (tr) to furnish with a thumb index

Etymology

Origin of thumb index

First recorded in 1900–05