(a.) Not usual; uncommon; rare; as, an unusual season; a person of unusual grace or erudition.

almost unheard-of atypical bizarre breakaway curious different eccentric exceptional extraordinary extremely freakish infrequent novel odd oddball offbeat original outlandish peculiar quaint queer rare rarely recherche remarkable scarce seldom met with seldom seen singular slow sparse strange sui generis uncommon uncommonly unconventional uncustomary undreamed-of unexpected unfamiliar unfrequent unheard-of unimaginable unique unordinary unorthodox unprecedented unthinkable unthought-of untypical unusually unwonted