from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The page size obtained by folding a whole sheet into four leaves.
- n. A book composed of pages of this size.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A size of paper (7.5"-10" x 10"-12.5")(190-254 x 254-312 mm). Formed by folding and cutting one of several standard sizes of paper (15"-20" x 20"-25")(381-508 x 508-635 mm) twice to form 4 leaves (eight sides).
- n. A book size, corresponding to the paper size.
from the GNU version of the Collaborative International Dictionary of English
- adj. Having four leaves to the sheet; of the form or size of a quarto.
- 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.
from The Century Dictionary and Cyclopedia
- n. A size of book in which the leaf is one fourth of a described or implied size of paper.
- Noting the size of a book in which a sheet makes four leaves: as, a quarto volume; being of the size or shape of the leaves of a quarto; as, quarto paper; a quarto edition.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the size of a book whose pages are made by folding a sheet of paper twice to form four leaves
Short for Middle English (in) quarto, (in) the fourth part (of a sheet), from Medieval Latin (in) quārtō, from Latin, ablative of quārtus, fourth; see kwetwer- in Indo-European roots.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin quartus ("fourth") (Wiktionary)