My early months as a Christian were a joyous feast of fellowship. There was nothing I loved more than to be with my new brothers and sisters in Christ. Every believer I knew seemed so sanctified and intimate with the Savior. I actually felt intimidated by lives that were seemingly lived on another plane of righteousness to my own sinful struggles. But it didn’t take long before I discovered a sub-culture my Christian peers described as “backsliders.”
Few things can match the shock we experience when brought face to face with those who abandon the Christian faith. And there was nothing that could have prepared me for the grief of seeing hands once raised in worship, now deployed in satanic vices—backslidden from their former Christian faith.
I could not fathom why anyone would abandon eternal rewards for a short season of wicked pleasure. My Arminian pastor assured me that backsliding was the only possible explanation, and that our job was to “persuade these backsliders to come back to church and restore the salvation they’ve lost.”
Indeed some people were quite effective at retrieving backsliders and over the years I saw an endless stream of people who would gain their salvation, lose it, and re-gain it only to lose it again—rinse and repeat. My eyes were slowly opening to the reality that my church was actually a spiritual transit lounge for people in my city who periodically ventured into the kingdom of God. I could smell the problem but was unable to pinpoint the source. Did the Bible have an explanation?
“Backsliding” is an Old Testament term found in the prophetic books and used within the context of Israel’s unfaithfulness to God. John MacArthur describes it as “a word that the prophets used of apostate unbelievers.”  John MacArthur, The MacArthur Study Bible (Nashville: Thomas Nelson, 2006) Note on Proverbs 14:14. He concedes that Christians can backslide only in the sense that they “regress into a period of spiritual dullness or disobedience.” But he adds that such cases always incur God’s discipline (Hebrews 12:6–11) and produce repentance.  http://www.gty.org/resources/questions/QA116/can-a-true-christian-backslide
That idea captures what most Calvinists mean if they use the term “backslider.” There is much that could be said about what constitutes a spiritual lapse, or how far you can go before you go too far. But the important principle to grasp is that the backsliding of a believer is always temporary and always involves God’s chastening which in turn produces repentance. It never means that their salvation was temporarily lost. (For further reading on this subject I would recommend two of John’s articles: Does Scripture Leave Room for Carnal Christians? and How Far Can Christians Go in Sinning?).
John argues that “backsliding” can never refer to a person who professes faith in Christ but lives in a “perpetual state of willful rebellion or ungodly indifference.”  http://www.gty.org/resources/questions/QA116/can-a-true-christian-backslide Such people are not backsliding believers but rather false Christians who were never accepted by Christ in the first place (Matthew 7:21–23; 1 John 3:4–10).
The backsliding doctrine I had been taught was actually the result of false shepherds preaching a false gospel that demanded no repentance. The result was providing false pronouncements of salvation on false converts who were more than happy to march out the door and back into the arms of the world they still loved more than Christ. The apostle John nailed the issue when he said: “They went out from us, but they were not really of us; for if they had been of us they would have remained with us; but they went out, so that it would be shown that they all are not of us” (1 John 2:19). As Ray Comfort summarized; “It's those we erroneously call backsliders, who fall away, because they have never slid forward in the first place”.  Quoted from Ray Comfort’s Sermon, True and False Conversion. http://www.livingwaters.com/audio/way-of-the-master/true-and-false-conversion
Backsliding has become a theologically tragic Christian cliché—tragic because of the ways it impugns God’s character. It implicitly denies God’s sovereign power in regenerating sinners (Ezekiel 36:25–27), resurrecting them from being dead in sin (Ephesians 2:1) to a new and living creation in Christ (2 Corinthians 5:17). The idea that a Christian can backslide and lose his salvation also impugns Christ’s promise to eternally preserve the people He saves:
My sheep hear My voice, and I know them, and they follow Me; and I give eternal life to them, and they will never perish; and no one will snatch them out of My hand. My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of the Father’s hand. (John 10:27–29)
I’ll never forget John MacArthur’s simple and yet profound argument for the security of Christian salvation based on God’s power to keep His people—“If I could lose my salvation, I would.”  Quoted from John MacArthur’s sermon, The Saint’s Guarantee. http://www.gty.org/resources/sermons/65-15/the-saints-guarantee The very idea of keeping our salvation on the basis of our own efforts is as preposterous as the idea of attaining our salvation in the first place because of something we did.
The modern “backslider” cannot be persuaded back into a kingdom he never entered in the first place. He needs to be evangelized and called to repentance—like all unbelievers do. And if he repents, it should not be treated as a re-commitment to his salvation but rather as an outward sign of God’s inner saving work.