Adjective: tertiary 'tur-shee,e-ree [N. Amer], tur-shu-ree [Brit]Noun: Tertiary
- The geological period from approximately 65 million to 2.6 million years ago, marked by the development of mammals
"Many modern mammal groups evolved during the Tertiary period";
- Tertiary period
Derived forms: Tertiaries
See also: ordinal
Type of: geological period, period
Part of: Age of Mammals, Cainozoic, Cenozoic, Cenozoic era
Encyclopedia: Tertiary, or services sector