Definition of "Untouchable" :

noun: belongs to lowest social and ritual class in India

adjective: not capable of being obtained

"Untouchable resources buried deep within the earth."

adjective: (especially used in traditional Hindu belief of the lowest caste or castes) defiling

adjective: forbidden to the touch

"In most museums such articles are untouchable."

adjective: impossible to assail

adjective: beyond the reach of criticism or attack or impeachment

"For the first time criticism was directed at a hitherto untouchable target."