/fawr"tee ayt"moh/ , n. , pl. forty-eightmos for 2, adj.
n.
1. a book size of about 2 1 / 2 × 4 in. (6 × 10 cm), determined by printing on sheets folded to form 48 leaves or 96 pages. Abbr.: 48mo, 48°
2. a book of this size.
adj.
3. in forty-eightmo.
[ 1885-90; FORTY-EIGHT + -MO ]