often pronounced twelvemo and written as 12mo A small format book made from sheets folded to give twelve leaves: also used in a more general way of books under about 7 inches (18cm) tall
A size of paper, so called because it is originally made by folding and cutting a single sheet from a printing press into 12 leaves; (5 by 7¾ inches): 6.5 to 7.5 inches high, approximately 4.5 inches wide
a book format, gathering formed from paper sheet folded in half twice and then in thirds, and comprises twelve leaves or twenty-four pages, see book sizes and paper sizes
A book consisting of sheets each of which is folded into twelve leaves; hence, indicating, more or less definitely, a size of a book; usually written 12mo or 12°