Noun
a mark consisting of characters written on a book; used to indicate shelf location
Source: WordNetIn that email he included a picture of the new “tag” he’d applied to the spine, in which he’d written the call number with a fine-point sharpie. Source: Internet
The domestic conference call number is (800) 289-0448. Source: Internet
The teams designated by the color of their bandannas get their first clue and are off to find the next clue hidden in the book found by using the call number. Source: Internet