Similar to the term dogmatic atheist, except this atheist is more 'evangelical' in his efforts, and definitely more hardcore, and can be considered as an individual who has decided to declare war on 'believers'.
Not only does the atheist profess his disbelief in the existence of God, but goes out of his way to convert those who do to his way of thinking.
He will use ad hominem attacks against those who have faith and beliefs, questioning their sanity, their intelligence, etc
Atheist: I cannot believe in a God that for all intents and purposes has not been proven to exist, nor has He revealed himself to me in any way.
Evangatheist: You're nuts for believing in God. You're deluded. You should drop your silly beliefs. Your faith is unfounded and unproven and impractical. Your head is full of 'theo(logical)-toxins' and you need to be cured. You can't be very intelligent to believe in any Supreme Being.