heretic

/HH EH1 R AH0 T IH0 K/
noun
  1. 1

    Someone who believes contrary to the fundamental tenets of a religion they claim to belong to.

  2. 2

    Someone who does not conform to generally accepted beliefs or practices

adjective
  1. 1

    Heretical; of or pertaining to heresy or heretics.

Antonyms

Source: https://en.wiktionary.org/wiki/heretic