untouchable

Short definition from Wiktionary

Adjective

1. 1
   Not able to be touched.
2. 2
   Not able to be defeated or bested.

Noun

1. 1
   A criminal who is so well-connected that they cannot be harmed.
2. 2
   Synonym of outcast: a person excluded from society.
3. 3
   A member of the lowest and most discriminated caste in traditional Indian society.
4. 4
   A law enforcement agent immune to intimidation, bribery, or seduction.