en·an·ti·o·mer 
(ĭ-năntē-ə-mər)
(ĭ-năntē-ə-mər)n.
Either of a pair of molecules that are mirror images but cannot be superimposed on each other, and that rotate the plane of polarized light by an equal amount in opposite directions. Also called enantiomorph, optical isomer.
[Greek enantios, opposite; see ant- in the Appendix of Indo-European roots + -MER, isomer.]
en·an′ti·o·meric (-mĕrĭk) adj.