The size of a book whose pages are made by folding a sheet of paper three times to form eight leaves WordNet 3.0 & Open English WordNet

Octavo, a Latin word meaning "in eighth" or "for the eighth time", is a technical term describing the format of a book, which refers to the size of leaves produced from folding a full sheet of paper on which multiple pages of text were printed to form the individual sections of a book. Wikipedia

Technical term describing the format of a book. Wikipedia Disambiguation

Abbreviation of octavo, a book size. OmegaWiki

A sheet of paper 7 to 10 inches (17-25 cm) high and 4.5 to 6 inches (11-15 cm) wide, the size varying with the large original sheet used to create it, made by folding the original sheet three times to produce eight leaves. OmegaWiki

A book size, corresponding to the page size. Wiktionary

A sheet of paper 7 to 10 inches (= 17.78 to 25.4 cm) high and 4.5 to 6 inches (= 11.43 to 15.24 cm) wide, the size varying with the large original sheet used to create it. It is made by folding the original sheet three times to produce eight leaves. Wiktionary

Paper size. Wiktionary (translation)