The geometric property of a rigid object (or spatial arrangement of points or atoms) of being non-superposable on its mirror image; such an object has no symmetry elements of the second kind (a mirror plane, σ = S 1, a centre of inversion, i = S2, a rotation-reflection axis, S 2n). If the object is superposable on its mirror image the object is described as being achiral.
See also: handedness, superposability
Sources:
Blue Book, p. 479 (https://www.acdlabs.com/iupac/nomenclature/)
PAC, 1996, 68, 2193. 'Basic terminology of stereochemistry (IUPAC Recommendations 1996)' on page 2203 (https://doi.org/10.1351/pac199668122193)