momentous. (moʊmentəs ) adjective. If you refer to a decision, event, or change as momentous, you mean that it is very important, often because of the effects that it will have in the future . ...the momentous decision to send in the troops. Synonyms: significant, important, serious, vital More Synonyms of momentous.
Quality of being momentaneous. momentariness. The property of being momentary. Synonyms: transitoriness, temporariness, evanescence, fleetingness, fugitiveness, transience, ephemerality, impermanence, impermanency, transiency, brevity, ephemeralness, briefness, shortness, short-livedness, caducity, incorporeity, insubstantiality, disappearance, vanishing, evaporation, mutability, instability, volatility, fugacity, conciseness … more.