Doub'let, n.

(dŭb'let), n. [O. Fr. doublet, diminutive of double, double; Pr. doblier.]

1. Two of the same kind; a pair; a couple.
2. (Print.) A word or phrase unintentionally doubled, or set up the second time.
3. The inner garment of a man; a waistcoat or vest;—so called with respect to the cloak or outer garment, or from being double for warmth, or because it makes the dress double.
4. (Lapidary Work.) A counterfeit stone, composed of two pieces of crystal, with a color between them, so that they have the same appearance as if the whole substance of the crystal were colored.
5. (Opt.) An arrangement of two lenses for a microscope, designed to correct spherical aberration and chromatic dispersion, thus rendering the object more clear and distinct. Wollaston.