The word "jiffiest" is an informal term that means a very short amount of time. There are many synonyms that can be used in place of this word. One synonym is "instantly," meaning something happens immediately and without delay. Another synonym is "promptly," suggesting that something is done quickly and efficiently. "Swiftly" is another synonym that denotes speed and agility. "Quickly" and "rapidly" are two more synonyms that convey urgency and rapidity. "Expeditiously" and "pronto" are also synonyms that suggest haste and speed. Regardless of the synonym used, they all connote a sense of urgency, rapidity, and efficiency.