duodecimo

(noun)

noun

1. (paper, printing) A size of paper, so called because it is originally made by folding and cutting a single sheet from a printing press into 12 leaves; (5 by 7¾ inches): 6.5 to 7.5 inches high, approximately 4.5 inches wide.

2. A sheet or page of that size

3. (printing) A book having pages of that size