'Libretti' definitions:
- Libretto \Li*bret"to\ (l[i^]*br[e^]t"t[-o]; It.
l[-e]*br[asl]t"t[-o]), n.; pl. E. Librettos (-t[=o]z), It.
Libretti (-t[-e]). [It., dim. of libro book, L. liber. See
Libel.] (Mus.)
(a) A book containing the words of an opera or extended piece
of music.
(b) The words themselves.
[1913 Webster]