There are numerous synonyms for the phrase "gone in a flash." Some of the most commonly used words or phrases to describe something that is quick or sudden are rapid, fleeting, instantaneous, momentary, swift, sudden, and transitory. Other options include brief, passing, ephemeral, evanescent, short-lived, and volatile. Depending on the context, alternative phrases that can convey the same meaning include disappearing like magic, vanishing into thin air, in the blink of an eye, and like a shooting star. Whether describing the passing of time or the disappearance of something, there are many ways to convey the idea of something happening quickly or unexpectedly.