Does atheism define you?
Absolutely not. Atheism doesn't reflect something you are, it reflects something you are not. It is of no substance by itself. Not believing in something doesn't define who you are, just like not believing in fairies doesn't define who you are. Most people are "afairiest," in that they don't believe in fairies. Does your afairiesm define you? Of course not. Have you even heard of the term? Probably not, because it is as meaningless as the term atheism. We can have an individual term for every individual thing we don't believe exist. The list would be endless. Is this list of things we don't believe in what defines us? Of course not.
You may also happen to be a secularist, humanist, naturalist, materialist, skeptic, scientist, environmentalist, logician, universalist, pantheist, etc.. these things contribute to defining you, not atheism. Theists attempt to generalize atheists as being materialistic evolutionists and go so far as to confuse the two as being synonymous. This is as much of a blanket stereotype as saying all theists are fundamentalists. While many atheists accept evolution as being true given the overwhelming evidence, the term "atheist" does not necessitate that one take a stance FOR anything, it simply means that one doesn't believe there is a god or gods. The other stances I listed are expressions that could be considered FOR something, stances that actually do contribute to defining us.
So I wish people would stop using the term, "atheism," as being a position FOR something. If you want to talk about evolution, science, the environment, logic, reason, the universe, nature, moral values, etc... and a persons position FOR these things, use the correct terms, not atheism.