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]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "matriarchal":
   absolute, aristocratic, authoritarian, autocratic, autonomous,
   bureaucratic, civic, civil, constitutional, democratic, despotic,
   dictatorial, fascist, federal, federalist, federalistic,
   governmental, gubernatorial, heteronomous, matriarchic, monarchal,
   monarchial, monarchic, monocratic, official, oligarchal,
   oligarchic, parliamentarian, parliamentary, patriarchal,
   patriarchic, pluralistic, political, republican, self-governing,
   theocratic, totalitarian