WordNet sense 1 (the form of a word that is used to denote a singleton):

singular form

WordNet sense 2 (the single one of its kind):

unique

WordNet sense 3 (existing alone or consisting of one entity or part or aspect or individual):

single

WordNet sense 4 (unusual or striking):

remarkable

WordNet sense 5 (beyond what is ordinary or usual; highly unusual or exceptional or remarkable):

extraordinary

WordNet sense 6 (beyond or deviating from the usual or expected):

curious, funny, odd, peculiar, rum, rummy

WordNet sense 7 (being definitely out of the ordinary and unexpected; slightly odd or even a bit weird):

strange, unusual

WordNet sense 8 (being or characteristic of a single thing or person):

individual