untouchable vs impermissible

untouchable is a noun but impermissible is not a noun.

Word	Noun	Adjective	Verb	Adverb
untouchable	Yes	Yes	No	No
impermissible	No	Yes	No	No

untouchable (noun)	impermissible (noun)
belongs to lowest social and ritual class in India

untouchable (adjective)	impermissible (adjective)
forbidden to the touch	not permitted
impossible to assail	not allowable
beyond the reach of criticism or attack or impeachment
not capable of being obtained
(especially used in traditional Hindu belief of the lowest caste or castes) defiling