The Collaborative International Dictionary of English v.0.48:

Hexagonal \Hex*ag"o*nal\, a. [Cf. F. hexagonal.]
   Having six sides and six angles; six-sided.
   [1913 Webster]

   Hexagonal system. (Crystal.) See under Crystallization.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hexagonal
    adj 1: having six sides or divided into hexagons [syn:
           hexangular, hexagonal]