Webster's Revised Unabridged Dictionary · 1913

Decimosexto

Decimosexto , noun

[Prop., in sixteenth; from Latin decimus tenth + sextus sixth.]

A book consisting of sheets, each of which is folded into sixteen leaves; hence, indicating, more or less definitely, a size of book; -- usually written 16mo or 16°.

Decimosexto , adjective

Having sixteen leaves to a sheet; as, a decimosexto form, book, leaf, size.