Meaning of twentymo

twen•ty•mo

Pronunciation: (twen'tē-mō", twun'-), [key]
— n., pl. adj. -mos,
—n.
  1. a book size of about 3 × 5 in. (8 × 12 cm), determined by printing on sheets folded to form 20 leaves or 40 pages.
  2. a book of this size. Symbol: 20mo, 20°
—adj.
  1. in twentymo. Also called
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.