unbeliefEnglishOxford English Thesaurusunbelief noun a symptom of unbelief was an inability to pray: atheism, non-belief, agnosticism, heresy, apostasy, irreligion, heathenism, godlessness, nihilism, lack of faith; scepticism, cynicism, disbelief, incredulity, suspicion, distrust, mistrust, doubt, non-conviction, dubiety. ▷antonyms belief, faith.unbelief Oxford Dictionary of English