Source : Webster's Revised Unabridged Dictionary (1913)

Hexagon \Hex"a*gon\, n. [L. hexagonum, Gr. ? six-cornered; "e`x
   six (akin to E. six) + ? angle.] (Geom.)
   A plane figure of six angles.

   {Regular hexagon}, a hexagon in which the angles are all
      equal, and the sides are also all equal.

Source : WordNet®

hexagon
     n : a six-sided polygon