one-off
Pronunciation:
noun
Definitions
Something that is done, created, etc. only once, and often quickly, simply, or improvisationally.
Example: I'll put together a quick one-off as a sample so we can taste the recipe.
Something unique and remarkable.
Example: It is a one-off; there is nothing else like it.
adjective
Definitions
Occurring once, one-time, independent of any pattern.
Example: Seeing Halley's Comet is a one-off, once-in-a-lifetime opportunity.
Singular; unique; special; remarkable.