\Doub"let\, n. [In sense 3, OF. doublet; in sense 4, F.
doublet, dim. of double double. See {Double}, a.]
1. Two of the same kind; a pair; a couple.
2. (Print.) A word or words unintentionally doubled or set up
   a second time.
3. A close-fitting garment for men, covering the body from
   the neck to the waist or a little below. It was worn in
   Western Europe from the 15th to the 17th century.
4. (Lapidary Work) A counterfeit gem, composed of two pieces
   of crystal, with a color them, and thus giving the
   appearance of a naturally colored gem. Also, a piece of
   paste or glass covered by a veneer of real stone.
5. (Opt.) An arrangement of two lenses for a microscope,
   designed to correct spherical aberration and chromatic
   dispersion, thus rendering the image of an object more
   clear and distinct. --W. H. Wollaston.
6. pl. (See No. 1.) Two dice, each of which, when thrown, has
   the same number of spots on the face lying uppermost; as,
   to throw doublets.
7. pl. [Cf. Pr. doblier, dobler draughtboard.] A game
   somewhat like backgammon. --Halliwell.
8. One of two or more words in the same language derived by
   different courses from the same original from; as, crypt
   and grot are doublets; also, guard and ward; yard and
   garden; abridge and abbreviate, etc.