enantiomer

n. [ Gr. 'enanti`os opposite + -mer. ] (Chem.) either of a pair of optical isomers of a chemical substance whose molecules are mirror images of each other, i. e., are related to each other as a right-handed to a left-handed glove; -- meaningful only for structures which have internal asymmetry.
-- E*nan`ti*o*mer"ic, a. [PJC]