Source : Webster's Revised Unabridged Dictionary (1913)

Isosceles \I*sos"ce*les\, a. [L., fr. Gr. ?; 'i`sos equal + ?
   leg.] (Geom.)
   Having two legs or sides that are equal; -- said of a
   triangle.

Source : WordNet®

isosceles
     adj : (of a triangle) having two sides of equal length