1. （与大多数人观点不合的）异端的，旁门左道的
A belief or action that is heretical is one that most people think is wrong because it disagrees with beliefs that are generally accepted.
2. （与某一宗教教义严重不合的）异端的，异教的
A belief or action that is heretical is one that seriously disagrees with the principles of a particular religion.