1. a. Not permitted to be touched: an untouchable idol.
b. Not capable of being touched or reached: an untouchable tennis serve.
2. a. Not permitted to be discussed: an untouchable subject.
b. Not subject or susceptible to criticism, rebuke, or attack: an appointee who was untouchable because of his political connections.
c. Not capable of being affected, especially adversely: bacteria that are untouchable by an antibiotic.
d. Not permitted to be altered: an untouchable religious text.
e. Not capable of being rivaled or surpassed: an untouchable skier.
f. Baseball Not giving up any hits. Used of a pitcher.