tertiary tertiarian • tertiate · · · Info · Definitions · Synonyms · Characters · · tertiary · · Text Latin · · Script 8 · · Length Definitions · · · (noun) from 63 million to 2 million years ago. Synonyms: Tertiary, Tertiary period. · · Noun Definition 1 (adj) coming next after the second and just before the fourth in position. Synonyms: third, 3rd. · · Adjective Definition 1 Synonyms · · · third · · Synonym 1 3rd · · Synonym 2 Characters · · a latin small letter a U+0061 e latin small letter e U+0065 i latin small letter i U+0069 r latin small letter r U+0072 t latin small letter t U+0074 y latin small letter y U+0079