Basically a atheist who denies the reality of God, but feels the need to stand on a soap box and preach the wrong doings and fairy stories of Christians so much that they actually become more obnoxious than the Christian, rather than just accepting the fact that everyone has different beliefs.
Religious Person: I believe in God.
Atheist: Really? that's interesting. I don't personally but I'd love to sit down with you and discuss the issue sometime.
Religious Person: I be live in God.
Scanatheist: You be live in God? I don't believe in God and I have absolute faith in science because it's completely accurate and irrefutable.