Webster's Revised Unabridged Dictionary · 1913

Tertiary

Tertiary , adjective

[Latin tertiarius containing a third part, from tertius third: compare French tertiaire. See Tierce.]

1.
Being of the third formation, order, or rank; third; as, a tertiary use of a word. — Trench
2.
(Chemistry) Possessing some quality in the third degree; having been subjected to the substitution of three atoms or radicals; as, a tertiary alcohol, amine, or salt. Compare Primary, and Secondary.
3.
(Geology) Later than, or subsequent to, the Secondary.
4.
(Zoology) Growing on the innermost joint of a bird's wing; tertial; -- said of quills.
Collocations (4)
Tertiary age (Geology) , See under Age, 8.
Tertiary color , a color produced by the mixture of two secondaries. The so-called tertiary colors are citrine, russet, and olive. — Fairholt
Tertiary period (Geology) , (a) The first period of the age of mammals, or of the Cenozoic era. (b) The rock formation of that period; -- called also Tertiary formation. See the Chart of Geology.
Tertiary syphilis (Medicine) , the third and last stage of syphilis, in which it invades the bones and internal organs.

Tertiary ({not transcribed}) , noun

1.
(Roman Catholic Church) 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
2.
(Geology) The Tertiary era, period, or formation.
3.
(Zoology) One of the quill feathers which are borne upon the basal joint of the wing of a bird. See Illust. of Bird.