The Collaborative International Dictionary of English v.0.48:
Tertiary \Ter"ti*a*ry\, a. [L. tertiarius containing a third
part, fr. tertius third: cf. F. tertiaire. See Tierce.]
1. Being of the third formation, order, or rank; third; as, a
tertiary use of a word. --Trench.
2. (Chem.) 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. Cf.
Primary, and Secondary.
3. (Geol.) Later than, or subsequent to, the Secondary.
4. (Zool.) Growing on the innermost joint of a bird's wing;
tertial; -- said of quills.
Tertiary age. (Geol.) 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. (Geol.)
(a) The first period of the age of mammals, or of the
(b) The rock formation of that period; -- called also
Tertiary formation. See the Chart of Geology.
Tertiary syphilis (Med.), the third and last stage of
syphilis, in which it invades the bones and internal