Spiritual death is simply a separation from God at some level. When Adam sinned he placed a fence between God and himself. It was not necessarily a block wall of complete separation. The same is true for us. For those who will suffer the second death spoken of in Revelation 20:6, that separation will be complete and permanent. Matthew 27:46 And about the ninth hour Jesus cried out with a loud voice, saying, "Eli, Eli, lema sabachthani?" that is, "My God, my God, why have you forsaken me?" There was at that time a separation between God and Jesus. Jesus was the sacrifice for the sins of the world. God was not, could not be, with him there; Jesus was on His own. We have no idea, probably could not even begin to imagine what that separation, that spiritual death, was like. Clearly, it was more than simply the physical death of the body.