Being of the third formation, order, or rank; third; as, a tertiary use of a word.
- Third in place, order, degree, or rank.
- Of, relating to, or designating the short flight feathers nearest the body on the rear edge of a bird's wing.
- Chemistry Of or relating to salts of acids containing three replaceable hydrogen atoms.
- Chemistry Of or relating to organic compounds in which a group, such as an alcohol or amine, is bound to three nonelementary radicals.
- Of or belonging to the geologic time, system of rocks, or sedimentary deposits of the first period of the Cenozoic Era, characterized by the appearance of modern flora and of apes and other large mammals. See Table at geologic time.
- A tertiary feather.
- The Tertiary Period or its system of deposits.
- Roman Catholic Church A member of a religious Third Order.