le·vo·ro·ta·to·ry 
(lē′və-rōtə-tôr′ē) also le·vo·ro·ta·ry (-tə-rē)
(lē′və-rōtə-tôr′ē) also le·vo·ro·ta·ry (-tə-rē)adj. Symbol l-
Of or relating to an optically active substance that rotates the plane of polarized light to the left, or counterclockwise (when looking toward the light source): Only levorotatory amino acids are biologically active.