Source : Webster's Revised Unabridged Dictionary (1913)

Levorotatory \Le`vo*ro"ta*to*ry\ (-r[=o]"t[.a]*t[-o]*r[y^]), a.
   [Levo- + rotatory.] (Chem. & Physics)
   Turning or rotating the plane of polarization towards the
   left; levogyrate, as levulose, left-handed quartz crystals,
   etc. [Written also {l[ae]vorotatory}.]

Source : WordNet®

levorotatory
     adj : rotating to the left [syn: {levorotary}, {left-handed}]