Synonyms and related words :
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