The abbreviation for duodecimo, a book size created by folding a printed sheet into twelve leaves or twenty-four pages. It is traditionally used in library cataloging and bibliographic descriptions to quickly denote a book standing between 17.5 and 20 centimeters in height.
Heard on the job
Check the catalog card, it should be listed as a D if it's that small trim size.
Also heard as
- 12mo
- twelvemo