octodecimo
(ɒktəʊˈdɛsɪməʊ)
[For in octodecimo, from L. octodecimus eighteenth, as in octavo, duodecimo, etc.]
The size of a book, or of the page of a book, in which each leaf is one-eighteenth of a whole sheet; a book of this size. Abbrev. 18mo.
| 1858 O. W. Holmes Aut. Breakf.-T. (1883) 19 A little dark platoon of octo-decimos. |