A set of lettered grooves cut down the side of a book, especially a diary, address book, or dictionary, for easy reference.
（尤指日程记录簿或词典的）拇指索引，书边标目，切口索引
Example sentencesExamples
One of the key design elements of the brochure is the series of thumb indexes along the face of the book.
The Indexed Edition features 21 thumb indexes and comes in a gold-embossed, two-piece blue box.
Kent's volume is a good size for students starting out in homeopathy and has a thumb index for added ease of use.
These known stepped or thumb indexes are easily damaged by being folded or worn-out according to long time use and this spoils the beauty of the pocketbook and the atlas.
Color-coded main topic sections serve as thumb indexes and are coordinated to match the table of contents, making the sections very quick and easy to find.
Derivatives
thumb-indexed
adjectiveˈθʌmˌɪndɛkst
It is a vintage 1958 King James Version, gold-leafed, thumb-indexed and equipped with an extensive directory of useful topics.
Example sentencesExamples
The book is also thumb-indexed, which is nice, but I don't necessarily need it.
In grade school, I used an old thumb-indexed concise dictionary that was spiral bound.
Definition of thumb index in US English:
thumb index
nounTHəm ˈinˌdeksθəm ˈɪnˌdɛks
A set of lettered or marked grooves cut down the side of a book, especially a diary or dictionary, for easy reference.
（尤指日程记录簿或词典的）拇指索引，书边标目，切口索引
Example sentencesExamples
Kent's volume is a good size for students starting out in homeopathy and has a thumb index for added ease of use.
The Indexed Edition features 21 thumb indexes and comes in a gold-embossed, two-piece blue box.
One of the key design elements of the brochure is the series of thumb indexes along the face of the book.
Color-coded main topic sections serve as thumb indexes and are coordinated to match the table of contents, making the sections very quick and easy to find.
These known stepped or thumb indexes are easily damaged by being folded or worn-out according to long time use and this spoils the beauty of the pocketbook and the atlas.