The Collaborative International Dictionary of English v.0.48:

Patriarchal \Pa`tri*ar"chal\, a. [Cf. F. patriarcal.]
   1. Of or pertaining to a patriarch or to patriarchs;
      possessed by, or subject to, patriarchs; as, patriarchal
      authority or jurisdiction; a patriarchal see; a
      patriarchal church.
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   2. Characteristic of a patriarch; venerable.
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            About whose patriarchal knee
            Late the little children clung.       --Tennyson.
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   3. (Ethnol.) Having an organization of society and government
      in which the head of the family exercises authority over
      all its generations.
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   Patriarchal cross (Her.), a cross, the shaft of which is
      intersected by two transverse beams, the upper one being
      the smaller. See Illust. (2) of Cross.

   Patriarchal dispensation, the divine dispensation under
      which the patriarchs lived before the law given by Moses.
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WordNet (r) 3.0 (2006):

patriarchal cross
    n 1: a cross with two crossbars