The Collaborative International Dictionary
Twin \Twin\, a. [OE. twin double, AS. getwinne two and two, pl., twins; akin to D. tweeling a twin, G. zwilling, OHG. zwiniling, Icel. tvennr, tvinnr, two and two, twin, and to AS. twi- two. See Twice, Two.]
Being one of two born at a birth; as, a twin brother or sister.
Being one of a pair much resembling one another; standing the relation of a twin to something else; -- often followed by to or with.
--Shak.(Bot.) Double; consisting of two similar and corresponding parts.
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(Crystallog.) Composed of parts united according to some definite law of twinning. See Twin, n., 4.
Twin boat, or Twin ship (Naut.), a vessel whose deck and upper works rest on two parallel hulls.
Twin crystal. See Twin, n., 4.
Twin flower (Bot.), a delicate evergreen plant ( Linn[ae]a borealis) of northern climates, which has pretty, fragrant, pendulous flowers borne in pairs on a slender stalk.
Twin-screw steamer, a steam vessel propelled by two screws, one on either side of the plane of the keel.
Wiktionary
n. either of two separate crystals that share crystal lattice points in a symmetrical manner and intergrow
Usage examples of "twin crystal".
She looked over the room with its dark and glossy wainscoting, the glitter from the twin crystal chandeliers, the gleam from the silver on the antique sideboard, the sparkle of china and Waterford glass.