The phrase "lightning-swift" is often used to describe something that is extremely fast, like a bolt of lightning streaking across the sky. However, there are a variety of other words and phrases that can be used to convey a similar meaning. For example, "lightning-quick," "blindingly fast," "rapid-fire," "breakneck speed," and "supersonic" are all synonyms for "lightning-swift". These descriptive words and phrases can make your writing more dynamic and engaging, especially when describing action or movement. So the next time you need to describe something that's moving with lightning-swift speed, consider using one of these synonyms to add a bit of flair to your writing.