What is "opera flannel"

Opera \Op"er*a\ ([o^]p"[~e]r*[.a]), n. [It., fr. opera work, composition, opposed to an improvisation, fr. L. opera pains, work, fr. opus, operis, work, labor: cf. F. op['e]ra. See Operate.]

1. A drama, either tragic or comic, of which music forms an essential part; a drama wholly or mostly sung, consisting of recitative, arias, choruses, duets, trios, etc., with orchestral accompaniment, preludes, and interludes, together with appropriate costumes, scenery, and action; a lyric drama.

2. The score of a musical drama, either written or in print; a play set to music.

3. The house where operas are exhibited.

   Op['e]ra bouffe [F. op['e]ra opera + bouffe comic, It. buffo], Opera buffa [It.], light, farcical, burlesque opera.

   Opera box, a partially inclosed portion of the auditorium of an opera house for the use of a small private party.

   Op['e]ra comique [F.], comic or humorous opera.

   Opera flannel, a light flannel, highly finished.
   --Knight.

   Opera girl or Opera girls (Bot.), an East Indian plant ( Mantisia saltatoria) of the Ginger family, sometimes seen in hothouses. It has curious flowers which have some resemblance to a ballet dancer, whence the popular name. Called also dancing girls.

   Opera glass, a short telescope with concave eye lenses of low power, usually made double, that is, with a tube and set of glasses for each eye; a lorgnette; -- so called because adapted for use at the opera, theater, etc.

   Opera hat, a gentleman's folding hat.

   Opera house, specifically, a theater devoted to the performance of operas.

   Opera seria [It.], serious or tragic opera; grand opera.