4. (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 (Linnæa 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.
Twin, n. 1. One of two produced at a birth, especially by an animal
that ordinarily brings forth but one at a birth; — used chiefly in the
plural, and applied to the young of beasts as well as to human young.
2. pl. (Astron.) A sign and constellation of the zodiac; Gemini. See
Gemini.