Atheism defies definition past it's meaning, like EvF says. Atheists as a group, to include activists of any sort, do tend to follow patterns generally and I find it interesting the many parallels between this group and religious groups.
There are charismatic leaders who's words are widely read; shared ideals, a perfect truth as in the atheist statement: "atheism is the philosophical position that deities don't exist"; Atheists/ non/ anti religious activists feel the need to congregate in groups such as this; need to spread the message to the world so everyone can think the same as they do, to convery the religious to their way of thinking.
Fundamentalist would be the no holds barred brick wall individuals who, like their religious counterparts, defy all logic and refuse on principle to consider and opposition, having already made up their mind, or have had their minds made up for them, have been brainwashed.
There are charismatic leaders who's words are widely read; shared ideals, a perfect truth as in the atheist statement: "atheism is the philosophical position that deities don't exist"; Atheists/ non/ anti religious activists feel the need to congregate in groups such as this; need to spread the message to the world so everyone can think the same as they do, to convery the religious to their way of thinking.
Fundamentalist would be the no holds barred brick wall individuals who, like their religious counterparts, defy all logic and refuse on principle to consider and opposition, having already made up their mind, or have had their minds made up for them, have been brainwashed.