heretic
n.n. a person who has different religious beliefs from the ones their group officially accepts. In the past, this was a very serious crime.
n. a person who holds beliefs or opinions contrary to those accepted by a religious group or church. Historically associated with severe punishment or execution.
The king declared him a heretic for his new ideas.
During the Middle Ages, anyone who questioned the official church teachings was often labeled a heretic.
The philosopher was accused of being a heretic because his radical theories about the nature of the soul challenged the established doctrines of the time.
From Middle English heretyk, heretike, from Old French eretique, from Medieval Latin or Ecclesiastical Latin haereticus, from Ancient Greek αἱρετικός (hairetikós, “able to choose, factious”), itself from Ancient Greek αἱρέω (hairéō, “I choose”).