/ Dictionary / Index S Sejanus: Meaning and Definition of Find definitions for: Se•ja•nus Pronunciation: (si-jā'nus), [key] — n. d.a.d. 31, Roman politician, commander of praetorian guard, and conspirator in the reign of Emperor Tiberius. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sejant-erect Sejm Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language