The size (5 by 7 3/4 inches) of book pages formed by folding single sheets from a printing press into 12 leaves each.(noun)
A book composed of pages of this size.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "duodecimo" in a sentence
"_Inset_, the portion of a sheet cut off and inserted in folding certain sizes, such as duodecimo, &c. (see Fig. 4)."
"A "duodecimo" sheet has the pages arranged as at fig. 4."
""duodecimo," &c. These names signify the number of folds, and consequently the number of leaves the paper has been folded into."