That has no parallel, equal, or counterpart; unmatched
Having no precedent or parallel; unheard-of; novel
Showing a marked departure from previous practice; new:
The definition of rare is something that exists in limited quantities, that is unusually good, or meat that is not cooked until it is well done.
The definition of unique is one of a kind.
Serving to identify; distinguishing or characteristic:
Distinct among others of a kind:
Find another word for one-of-a-kind. In this page you can discover 8 synonyms, antonyms, idiomatic expressions, and related words for one-of-a-kind, like: unparalleled, unprecedented, original, rare, unique, distinctive, in a class by itself and special.