While a "wake-up call" is a popular phrase to refer to a sudden or startling realization, there are plenty of other synonyms that can be used to express the same idea. Some options include an awakening, a revelation, a rude awakening, a shock, a jolt, an eye-opener, a reality check, a reminder, or a warning sign. All of these terms can be used to describe a moment of clarity or a sudden realization that one has been living in a state of ignorance or complacency. Whether you prefer to use one of these synonyms or the original phrase, the important thing is to embrace the learning opportunity and to use it as a catalyst for positive change.