A substance that is capable of rotating plane-polarized light. Molecules of an optically active substance cannot be superimposed on their own mirror images, just as your left hand cannot be superimposed on your right when both are held palm-down.
OPTICAL ACTIVITY (OPTICALLY ACTIVE)
Meaning of OPTICAL ACTIVITY (OPTICALLY ACTIVE) in English
General chemistry English glossary. Английский глоссарий общей химии. 2012