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Synonyms for Unique (same or very similar meaning)

WordNet sense 1 (the single one of its kind):

WordNet sense 2 (existing alone or consisting of one entity or part or aspect or individual):

WordNet sense 3 (radically distinctive and without equal):
alone, unequaled, unequalled, unparalleled

WordNet sense 4 (such that comparison is impossible; unsuitable for comparison or lacking features that can be compared):
incomparable, uncomparable

From the ODE community, based on WordNetadd/edit