octavo

/AA1 K T IH0 V OW0/
noun
  1. 1

    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.

  2. 2

    A book of octavo pages.

Source: https://en.wiktionary.org/wiki/octavo