Doublet \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.

Source: Webster's Revised Unabridged Dictionary (1913)