Also found in: Acronyms.
n. pl. oc·to·dec·i·mos
1. The page size, 4 by 6.5 inches, of a book composed of printer's sheets folded into 18 leaves or 36 pages.
2. A book composed of octodecimo pages. In both senses also called eighteenmo.
n, pl -mos
(Printing, Lithography & Bookbinding) bookbinding another word for eighteenmo
[C18: from New Latin phrase in octodecimo in an eighteenth (of a whole sheet)]