What is apostasy (John 15) in Lutheranism?

In contrast to the *Reformed* tradition, it it the best of my understating, that Lutherans hold in election unto salvation for all who all in Christ, yet also hold that individuals, because of their own fault and will, can turn away fro the faith and lose their salvation. This being the reason for all the warnings and admonitions in the Bible. One example would be John 15, where Jesus says that anyone who does not abide in his word, will be cut off. Given all that, what does apostasy mean in Lutheranism? Is it someone who utterly rejects Christ, or is it anyone caught up in habitual sin, like for example adultery or gambling, etc.