“Unique” is an absolute adjective that means “unlike any other.” One is either like another or not like another; one cannot be very much like another. (One can be like another in many ways, but that goes beyond the definition of this word.)
A new meaning of “unique” has developed: the definition of this word has come to include “unusual,” which is not absolute and can be modified in a comparative manner. However, the writers of standardized examinations do not consider this definition to be standard American English. Students taking these tests are expected to recognize that modifying the word “unique” in this manner is an error to be identified and corrected.
