unrepeatable
Definitions
Impossible to repeat or duplicate.
Unique and incapable of being experienced or produced a second time.
Too offensive or improper to be spoken aloud.
Examples
The sunset over the canyon was an unrepeatable experience that I will cherish forever.
The athlete achieved an unrepeatable feat by breaking three world records in a single afternoon.
Synonyms
unique one-off singular irreplaceable non-recurrent once-in-a-lifetime