The Collaborative International Dictionary of English v.0.48:

Dominican \Do*min"i*can\, prop. a. [NL. Dominicanus, fr.
   Dominicus, Dominic, the founder: cf. F. Dominicain.]
   Of or pertaining to St. Dominic (Dominic de Guzman), or to
   the religious communities named from him.
   [1913 Webster]

   Dominican nuns, an order of nuns founded by St. Dominic,
      and chiefly employed in teaching.

   Dominican tertiaries the third order of St. Dominic. See
      Tertiary.
      [1913 Webster]