What Paul describes here is the condition of our spiritual death. Spiritual death is somewhat different from physical death. When we die physically, our body is not able to do anything. There is no animating energy left in our body to do anything, even to breathe. But the way Paul describes our spiritual death is anything but inactive and impotent. One who is spiritually dead is very active: he is busy walking, following the course of this world, following Satan; he is busy living in the passions of his flesh, carrying out the desires of the body and the mind. So, in what sense is a person spiritually dead?
The Bible speaks of three different kinds of death: physical death, spiritual death and eternal (or second) death. I mention these different kinds of death because, for man, death is not the end of his existence. For sure, man is not eternal because he is not self-existent as God is; he is created. Man is immortal, however--that is, he never goes out of existence once he is born. Death for man, then, is not the end of his existence. Death is to be separated from the source of life. So, physical death is for our body to be separated from the source of its life--our soul/spirit. Spiritual death is for our spirit to be separated from its source of life--God. And eternal (or, second) death is for the whole man to be separated from God forever, both in body and soul.