"Unmissable" is often used to describe something that cannot be missed or overlooked due to its significant importance or uniqueness. However, there are several other synonyms that can be used to convey the same message. One such word is "imperative," meaning essential or necessary. Another option is "indispensable," which implies that something is absolutely necessary and cannot be done without. "Unforgettable" and "memorable" are other alternatives that indicate something is worth experiencing or witnessing. Lastly, "must-see" or "must-do" also convey that something is highly recommended and not to be missed. Overall, there are numerous alternative words available to replace "unmissable" and still convey the same idea.