eighteenmo

eight·een·mo

E0059900 (ā-tēn′mō)n. pl. eight·een·mos See octodecimo.
[From 18mo, abbr. of octodecimo.]

eighteenmo

(ˈeɪˈtiːnməʊ) n, pl -mos1. (Printing, Lithography & Bookbinding) Also called: octodecimo a book size resulting from folding a sheet of paper into 18 leaves or 36 pages. Often written: 18mo or 18° 2. (Printing, Lithography & Bookbinding) a book of this size