Definitions
1.nounA book size using duodecimo-sized pages.
2.nounA size of paper, so called because it is originally made by folding and cutting a single sheet from a printing press into 12 leaves; (5 by 7¾ inches): 6.5 to 7.5 inches high, approximately 4.5 inches wide.
3.nounA sheet or page of that size.
4.nounA book having pages of that size.