/siks'tee fawr"moh, -fohr"-/ , n. , pl. sixty-fourmos , adj.
n.
1. a book size (about 2 × 3 inches; 5 × 7 cm) determined by printing on sheets folded to form 64 leaves or 128 pages.
2. a book of this size. Symbol: 64mo, 64°
adj.
3. printed, folded, or bound in sixty-fourmo.
[ SIXTY-FOUR + -MO ]