Pronunciation: (siks'tēn'mō), [key]
—n., pl. -mos,
1. Also called sextodecimo. a book size (about 4×6 in.; 10×15 cm) determined by printing on sheets folded to form 16 leaves or 32 pages.
2. a book of this size. Symbol: 16mo, 16°
printed, folded, or bound in sixteenmo; sextodecimo.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.