The Collaborative International Dictionary of English v.0.48:

Patriarchy \Pa"tri*arch`y\, n. [Gr. patriarchi`a.]
   1. The jurisdiction of a patriarch; patriarchship.
      --Brerewood.
      [1913 Webster]

   2. Government by a patriarch; patriarchism.
      [1913 Webster]

WordNet (r) 3.0 (2006):

patriarchy
    n 1: a form of social organization in which a male is the family
         head and title is traced through the male line [syn:
         patriarchy, patriarchate]