unique

adjective

1. 1

   highly unusual or rare but not the single instance

   spoke with a unique accent

   had unique ability in raising funds

2. 2

   radically distinctive and without equal

   he is alone in the field of microbiology

   this theory is altogether alone in its penetration of the problem

3. 3

   (followed by `to') applying exclusively to a given category or condition or locality

   a species unique to Australia

4. 4

   the single one of its kind

   a singular example

   the unique existing example of Donne's handwriting