(a.) Very important; weighty; as, a momentous decision; momentous affairs\.

absolute ascendant authoritarian authoritative authorized autocratic big big-league big-name big-time bigwig bigwigged bustling charged charismatic charming clothed with authority commanding competent consequential considerable controlling critical crucial decisive dominant double-barreled duly constituted earthshaking effective effectual efficacious eminent empowered enchanting epochal estimable eventful ex officio fraught full of incident governing grand grave great heavyweight hegemonic hegemonistic high-powered imperative important influential laden leading magnetic major material meaningful mighty monocratic name of concern official personable persuasive phenomenal pivotal portentous potent powerful preeminent prestigious prominent puissant ranking reputable ruling self-important senior serious significant stirring strong suasive substantial superior supreme telling totalitarian vital weighty winning world-shaking