doublet

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A close-fitting jacket, with or without sleeves, worn by European men from the late 1300s to around 1650.
• noun A pair of similar or identical things.
• noun A member of such a pair.
• noun Physics A multiplet with two members.
• noun Linguistics One of two words derived from the same historical source by different routes of transmission, such as skirt from Scandinavian and shirt from English.
• noun An imitation gem composed of two parts, as of an inferior stone layered beneath a precious gem.
• noun Games A throw of two dice in which the same number of dots appears on the upper face of each.

from The Century Dictionary.

• noun In organ-building, a two-feet stop, or fifteenth. See stop, 6.
• noun One of a pair of like things; a duplicate: in most uses commonly in the plural.
• noun Specifically— In typography, an unintentional duplication of a word, phrase, passage, etc. Also double.
• noun In philology, a duplicate form of a word; one of two (or, by extension, three or more) words originally the same, but having come to differ in form, and usually more or less in meaning. Doublets are very common in English. They usually consist of an older and a later form, the older being generally descended and the later directly borrowed from the same original (as benison, benediction; malison, malediction, etc.), or two accidental variations of one original, sometimes slightly discriminated (as alarm, alarum, etc.), or of a standard literary and a dialectal form (as church, kirk; lord, laird, etc.). See dimorphism, 5.
• noun In heraldry, a chevron-shaped bearing which issues from either side of the field, and reaches nearly to the opposite side without touching it.
• noun One of a pair of dice turned up in throwing when they both present the same number of spots: usually in the plural: as, to throw doublets.
• noun Something formed by a union of two like things; a duplicate combination.
• noun In optics, a combination of two simple lenses, with the object of diminishing the chromatic and spherical aberration: in the former use called specifically an achromatic doublet. The Wollaston doublet (see the extract) consists of two plano-convex lenses placed a short distance apart in the eyepiece of a microscope.
• noun plural A game with dice upon tables, somewhat resembling backgammon.
• noun An outer body-garment such as was worn by men from about the end of the fifteenth until about the middle of the seventeenth century.

from the GNU version of the Collaborative International Dictionary of English.

• noun Two of the same kind; a pair; a couple.
• noun (Print.) A word or words unintentionally doubled or set up a second time.
• noun 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.
• noun (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.
• noun (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.
• noun Two dice, each of which, when thrown, has the same number of spots on the face lying uppermost.
• noun A game somewhat like backgammon.
• noun One of two or more words in the same language derived by different courses from the same original from

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a man’s close-fitting jacket, with or without sleeves. Men in Europe wore doublets from the 1400s to the 1600s.
• noun a pair of two similar or equal things; couple.
• noun linguistics one of two or more different words in a language derived from the same origin but coming by different routes (e.g., toucher and toquer in French or yard and garden in English).
• noun literature In textual criticism, two different narrative accounts of the same actual event.
• noun An imitation gem made of two pieces of glass or crystal with a layer of color between them.
• noun printing, US A word or phrase set a second time by mistake.
• noun quantum mechanics A quantum state of a system with a spin of 1/2, such that there are two allowed values of the spin component, -1/2 and +1/2.
• noun computing A word (or rather, a halfword) consisting of two bytes
• noun botany A very small flowering plant, Dimeresia howellii
• noun A word ladder puzzle.
• noun 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.
• noun Either of two dice, each of which, when thrown, has the same number of spots on the face lying uppermost.
• noun uncountable A game somewhat like backgammon.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a man's close-fitting jacket; worn during the Renaissance