4to 4th • 4wd · · · Info · Definitions · Synonyms · Characters · · 4to · · Text Common · · Latin · · Scripts 3 · · Length 1 · · Syllables Definitions · · · (noun) the size of a book whose pages are made by folding a sheet of paper twice to form four leaves. Synonyms: quarto. · · Noun Definition 1 Synonyms · · · quarto · · Synonym 1 Characters · · 4 digit four U+0034 o latin small letter o U+006F t latin small letter t U+0074