Tĕr'ti-a-ry, a.

(tēr'shĭ-a-rў, 44, 95), a. [Lat. tertiarius, from tertius, the third; Fr. tertiaire.] Of the third formation, order, or rank; third; as, a tertiary use of a word. [Rare.] Trench.

Tertiary color, a color produced by the mixture of two secondaries. “The so-called tertiary colors are citrine, russet, and olive.” Fairholt.—Tertiary epoch. (Geol.) (a.) The first period of the age of mammals, or of the cenozoic era. (b.) The rock-formation of the period;—called also tertiary formation. See GEOLOGY.