IPA: /ʌnˈmɪsəbl/
KK: /ʌnˈmɪsəbl/
Something that is so good or important that you must see or experience it.
The concert was unmissable; everyone talked about it for weeks.
Unmissable → It is formed from "un-" (meaning not) and "missable" (from the verb "miss" which comes from Old English "missan", meaning to fail to hit, reach, or come into contact with). The word "unmissable" means something that cannot be missed or overlooked.
Think of 'not' ('un-') being added to 'missable', which means something that can be missed. So, if something is 'unmissable', it means you definitely won't want to miss it!