One who does not hold a belief in a higher power of any kind. One who chooses to control their own destiny and not rely on a mythical figure to do it for them. Contrary to belief, Atheists are not Satan worshipping heathens, as one would have to have a belief in God in order to believe that Satan exists.
Jane does not pray, go to church, or celebrate Christmas. She is an atheist and feels that participating in the affore mentioned activities would make her a hypocrite.