The Collaborative International Dictionary of English v.0.48:

Tertiary \Ter"ti*a*ry\, n.; pl. Tertiaries.
   1. (R. C. Ch.) A member of the Third Order in any monastic
      system; as, the Franciscan tertiaries; the Dominican
      tertiaries; the Carmelite tertiaries. See Third Order,
      under Third. --Addis & Arnold.
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   2. (Geol.) The Tertiary era, period, or formation.
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   3. (Zool.) One of the quill feathers which are borne upon the
      basal joint of the wing of a bird. See Illust. of Bird.
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