/twen"tee moh', twun"-/ , n. , pl. twentymos , adj.
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.
3. in twentymo. Also called vigesimo .
[ 1835-45; TWENTY + -MO ]