An Atheist who is deliberately angry at all religious people for no legitimate reason. An Angry Atheist will often write books, create YouTube videos, or film documentaries with the purpose of destroying others' religious beliefs. An Angry Atheist will pretend to have the authority of science and history on their side, but will immediately reject any science or history that supports the claims of a given religion, with the accusation that it is "biased" or "un-intellectual".
Oftentimes, the Angry Atheist has been brought up with a religious mindset (usually Christian) which he/she has abandoned for intellectual/emotional reasons. But the painful feeling of having been raised on "lies" and "fairy-tales" has left the person very bitter toward all religions and religious people. And therefore, the Angry Atheist will essentially pick fights for philosophical vengeance, targeting religious laypeople and often avoiding debates with intelligent religious leaders capable of destroying their arguments.
An unfortunate side-effect of this out-going hostility, is that religious people will often attribute the attitudes of this minority to all Atheists, causing a negative stereotype to be formed.
Some examples of Angry Atheists include Richard Dawkins (author of The God Delusion), Sam Harris (author of The End of Faith), Friedrich Nietzsche (Atheist Existentialist who was the first to suggest that, "God is Dead"), and Brian Flemming (filmmaker behind The God Who Wasn't There documentary).
Someone who has the guts to stand up to and criticize some aspects of religion, which for some reason or another remains a complete taboo in our society.
Notice how critics of capitalism aren't called "angry socialists", critics of modern liberalism aren't (or at least shouldn't be) called angry conservatives, etc.
Whenever someone deals with religion, however, he must don kid gloves.
Of course, there will always be those immature twats who take it to the extreme- i admit Brian Flemming is probably one of them. But you still shouldn't discount every one of their messages - keep an open mind! (though not too much so)
It should be noted that the vast majority of religion-critics don't "hate" religion - they're just tired of its near-immunity to criticism and debate.
Outside of religion, cutting off a baby boy's foreskin is most often seen as despicable and wrong. But once the protective shelter of faith is granted, it becomes a taboo to say anything about it.
Another example: the drug peyote is normally illegal, but some native americans out west are allowed to use it for one of their religious rituals - also, voodoo worshippers of a certain haitian-american sect are allowed to sacrifice certain animals (i'm not making this up)
It's weird how the moment the "faith" cover is given, a person's actions are suddenly almost off limits. Somehow, we've just agreed as a society that that's how we should work. And anyone who questions this norm is quickly labeled an "angry atheist".
Odd, don't ya think?