sextodecimo
/ˌsɛkstə(ʊ)ˈdɛsɪməʊ
/(abbreviation 16mo)
noun (plural sextodecimos)
1A size of book page that results from folding each printed sheet into sixteen leaves (thirty-two pages).
1.1A book of sextodecimo size.
Origin
Late 17th century: from Latin sexto decimo, ablative of sextus decimus 'sixteenth'.