/ Dictionary / Index T therian: Meaning and Definition of Find definitions for: the•ri•an Pronunciation: (thēr'ē-un), [key] — adj. (in some classification systems) belonging or pertaining to the group Theria, comprising the marsupial and placental mammals and their extinct ancestors. —n. a therian animal. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. theriac therianthropic Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language