\Dec`i*mo*sex"to\, n. [Prop., in sixteenth; fr. L.
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[deg].

\Dec`i*mo*sex"to\, a.
Having sixteen leaves to a sheet; as, a decimosexto form,
book, leaf, size.