What does "4to" mean?

Abbreviation of quarto, a paper size.

What is a synonym for "4to"?

Common synonyms include: quarto.

noun

noun ·Rare ·Advanced level

Noun

1
Abbreviation of quarto, a paper size. abbreviation, alt-of, countable, uncountable
2
the size of a book whose pages are made by folding a sheet of paper twice to form four leaves wordnet
3
Abbreviation of quarto, a corresponding book size. abbreviation, alt-of, countable, uncountable

From Latin quārtō, ablative case singular of quārtus (“fourth”).