The Collaborative International Dictionary of English v.0.48:
matriarchal \ma`tri*ar"chal\, a. Of or pertaining to a matriarch; governed by a matriarch or matriarchs; as, a matriarchal society. [1913 Webster +PJC]WordNet (r) 3.0 (2006):
matriarchal adj 1: characteristic of a matriarchy [ant: patriarchal]