optical activity

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A property caused by asymmetric molecular structure that enables a substance to rotate the plane of incident polarized light.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) the ability of a chemical compound to rotate the plane of plane-polarized light. This is found only in chemicals whose molecular structure does not have a plane of symmetry, and is common in biochemical compounds.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics a property caused by asymmetrical molecular or crystal structure that enables a compound or crystal to rotate the plane of incident polarized light
• noun chemistry A measure of the amount of optical rotation produced by a standard amount of a substance