The modification of an object which results in the loss of one or more symmetry elements, such as those which preclude
chirality (mirror plane, centre of
inversion, rotation-reflection axis), as in the conversion of a
prochiral molecular entity into a
chiral one.
Source:
PAC, 1996, 68, 2193
(Basic terminology of stereochemistry (IUPAC Recommendations 1996))
on page 2205