Twin″ning (?), n.(Crystallog.) The assemblage of two or more crystals, or parts of crystals, in reversed position with reference to each other in accordance with some definite law; also, rarely, in artificial twinning (accomplished for example by pressure), the process by which this reversal is brought about.
Polysynthetic twinning, repeated twinning of crystal lamellæ, as that of the triclinic feldspars. — Repeated twinning, twinning of more than two crystals, or parts of crystals. — Twinning axis, Twinning plane. See the Note under Twin, n.