- a book size (about 2 × 3 inches; 5 × 7 cm) determined by printing on sheets folded to form 64 leaves or 128 pages.
- a book of this size. Symbol: 64mo, 64°
- printed, folded, or bound in sixty-fourmo.
Origin of sixty-fourmo
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- a book size resulting from folding a sheet of paper into 64 leaves or 128 pages, each one sixty-fourth the size of the sheetOften written: 64mo, 64°
- a book of this size