thumb index

1. 1.

   one of a series of rounded notches in the fore edge of a book to indicate sections

   Broadernotch

Questions about thumb index

What does thumb index mean?

thumb index means "one of a series of rounded notches in the fore edge of a book to indicate sections".

Is thumb index a common word?

thumb index is banded "Rare" — specialist or archaic — most readers will not have met it. The band comes from how often the word appears in a large corpus of everyday English, not from an editor's impression.