1. A Christian Atheist
2. One who is raised as a Christian, but then through life, learning, science, etc becomes a atheist. While still retaining some Christian believes and all previous knowledge.
3. One who understands aligns their views somewhat with Christianity, but does not believe in it themselves. Nor any other religion.
I was born and raised as a Christian. Then later in life I became an atheist. Now I am a Chratheist.
Look at those Cratheists over there, wearing crosses and burning a bible.