Backsliding is a word used by Christians when people fall away from the faith. The adjective form is “backslidden,” the present participle is “backsliding,” and if you want to sound southern about it the past participle is “backslid.”
This word isn’t used in many contexts outside of Christianity with the prominent exception of a Rancid song. Christian musicians who question their beliefs seem to gain the most notoriety. Nefarious musical backsliders include Amy Grant, Bob Dylan, Kris Kristofferson and David Bazan.
Christian culture views backsliding as something that can be prevented by one’s earnest efforts. (In Christian culture, most faith-related things should involve earnest effort.) Backsliding isn’t viewed with much clemency or seen as a valid and perhaps vital part of someone’s spiritual journey. Ergo, 10 handy steps to stave away backsliding can be found by clicking here.
Those who admit to faltering faith typically receive a healthy dollop of rebuke and admonition from the Christian culture, followed by an urging to “do what’s right.” The notion that they are doing right by themselves and by God in being honest about their misgivings has little if any validity in Christian culture. But if the Bible is true then the God of the Bible can withstand questioning and even demands it. He blessed Jacob after Jacob wrestled with him and he didn’t promise to spit his naysayers out of his mouth, only the lukewarm. Christian culture doesn’t know quite what to do with this. Be warned that if you express your doubts or struggles to someone enmeshed in Christian culture these will be met with disapproval and handled with severity.