quarto

What it means

1. countableuncountablepaperA size of paper (7.5"-10" x 10"-12.5" or 190-254 x 254-312 mm). Formed by folding and cutting one of several standard sizes of paper (15"-20" x 20"-25" or 381-508 x 508-635 mm) twice to form 4 leaves (eight sides).
   1. UKcountableuncountablepaperQuarto writing paper (10 inches x 8 inches)
2. countableuncountablemediaA book size, corresponding to the paper size.

   Beneath an old ebony table were two long carved oak chests. I lifted the lid of one, and at the top was a once-white surplice covered with dust, and beneath was a mass of tracts — Commonwealth Quartos, unbound — a prey to worms and decay.

   1880, William Blades, The Enemies of Books, page 40

   Synonyms: 4to, 4º, Q

In a sentence

Beneath an old ebony table were two long carved oak chests. I lifted the lid of one, and at the top was a once-white surplice covered with dust, and beneath was a mass of tracts — Commonwealth Quartos, unbound — a prey to worms and decay.

1880, William Blades, The Enemies of Books, page 40

Where it comes from

1. Latinquartus“fourth”
2. Englishquarto

From Latin quartus (“fourth”).