quarto Meaning, Definition & Usage

  1. noun the size of a book whose pages are made by folding a sheet of paper twice to form four leaves
    4to.

WordNet

Quar"to adjective
Etymology
L. in quarto in fourth, from quartus the fourth: cf. F. (in) quarto. See Quart.
Definitions
  1. Having four leaves to the sheet; of the form or size of a quarto.
Quar"to noun
Wordforms
plural Quartos
Definitions
  1. 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.

Webster 1913