The Collaborative International Dictionary of English v.0.48:

Patonce \Pa*tonce"\ (p[.a]*t[o^]ns"), a. [Cf. F. patte d'once
   paw of an ounce.] (Her.)
   Having the arms growing broader and floriated toward the end;
   -- said of a cross. See Illust. 9 of Cross.
   [1913 Webster]