Defn: 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
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.)
Defn: A sign and constellation of the zodiac; Gemini. See Gemini.
3. A person or thing that closely resembles another.
4. (Crystallog.)
Defn: A compound crystal composed of two or more crystals, or parts of crystals, in reversed position with reference to each other.
Note: The relative position of the parts of a twin may be explained by supposing one part to be revolved 180º about a certain axis (called the twinning axis), this axis being normal to a plane (called the twinning plane) which is usually one of the fundamental planes of the crystal. This revolution brings the two parts into parallel position, or vice versa. A contact twin is one in which the parts are united by a plane surface, called the composition face, which is usually the same as the twinning plane. A penetration twin is one in which the parts interpenetrate each other, often very irregularly. Twins are also called, according to form, cruciform, geniculated, etc.
TWIN
Twin, v. i. [imp. & p. p. Twinned; p. pr. & vb. n. Twinning.]