a religious belief or doctrine contrary to or incompatible with an explicit Church dogma, esp Christian doctrine
Heresy arises because organized religion tends to define its experience in terms of creeds or accepted statements of belief. Such statements set the boundaries of each religious group, within which those who reject the formal doctrines, or who hold beliefs deemed contrary to them, are termed heretics, and may be expelled or persecuted from the group. What counts as heresy may change, if what is accepted as orthodoxy is redefined — Dr Mel Thompson
adherence to an opinion or doctrine contrary to generally accepted belief
[Middle English heresie via Old French and late Latin from Greek hairesis action of taking, choice, sect, from hairein to take]