An almost imperceptible space of time. See Synonyms at moment. A particular or precise time: at the instant of combustion. The current month: your letter of the 15th instant. A food or beverage designed for quick preparation. Occurring at once; immediate: instant gratification. Imperative; urgent: an instant need. Now under consideration; present. Commercially prepared or processed for quick and easy final preparation: an instant cake mix. Readily soluble in water: instant coffee; instant powdered milk. Appearing, done, or taking place with or as if with maximum quickness and ease: "She had the gift of instant intimacy\u201d ( Sylvia Jukes Morris). At once; instantly.