"Give a start" is a common phrase used to describe a sudden reaction or shock caused by something unexpected or surprising. However, there are many synonyms that can be used to express the same idea, such as "startle", "surprise", "jolt", "shock", "upset", "rattle", or "frighten". These words convey a sense of being caught off guard or feeling unsettled by an unforeseen event. They can also be used to describe a sudden physical or emotional response to a certain stimulus. By using these synonyms, writers and speakers can add variety and depth to their language, making their message more impactful and engaging.