Source : Webster's Revised Unabridged Dictionary (1913)

Levorotation \Le`vo*ro*ta"tion\, n. [Written also
   {l[ae]vorotation}.] [Levo- + rotation.] (Physics & Chem.)
   Rotation in the direction of an outgoing right-handed screw;
   counter-clockwise rotation; -- applied chiefly to the turning
   of the plane of polarization of light.