Quarto
WordNet
noun
(1) The size of a book whose pages are made by folding a sheet of paper twice to form four leaves
WiktionaryText
Noun
- A size of paper (7.5"-10" x 10"-12.5")(190-254 x 254-312 mm). Formed by folding and cutting a standard large sheet of paper (15"-20" x 20"-25")(381-508 x 508-635 mm) twice to form 4 leaves (eight sides).
- A book size, corresponding to the paper size.