Source : Webster's Revised Unabridged Dictionary (1913)

Canthus \Can"thus\, n.; pl. {Canthi}. [NL., fr. Gr. ?.] (Anat.)
   The corner where the upper and under eyelids meet on each
   side of the eye.

Source : WordNet®

canthus
     n : either of the corners of the eye where the upper and lower
         eyelids meet
     [also: {canthi} (pl)]