Quarto
From BiblePortal Wikipedia
Webster's Dictionary [1]
(1): ( n.) Originally, a book of the size of the fourth of sheet of printing paper; a size leaves; in present usage, a book of a square or nearly square form, and usually of large size.
(2): ( a.) Having four leaves to the sheet; of the form or size of a quarto.
The Nuttall Encyclopedia [2]
A book having the sheet folded into four leaves.
