Nouns

(n)untouchable, Harijanbelongs to lowest social and ritual class in India

Adjectives

(s)untouchablebeyond the reach of criticism or attack or impeachment“for the first time criticism was directed at a hitherto untouchable target” (Newsweek)
(s)unassailable, untouchableimpossible to assail
(s)untouchableforbidden to the touch“in most museums such articles are untouchable”
(s)untouchable(especially used in traditional Hindu belief of the lowest caste or castes) defiling
(s)inaccessible, unobtainable, unprocurable, untouchablenot capable of being obtained“a rare work, today almost inaccessible”, “timber is virtually unobtainable in the islands”, “untouchable resources buried deep within the earth”