Recently I have been involved in some discussions with people regarding atheism. On one side of the discussion are Christians and other religious people. By and large they posit the aforementioned definition of atheism. On the other side of the discussion, however, are some atheists. By and large they view their atheism as a lack of belief, rather than a belief.
Admittedly, I am speaking in generalities and have failed to provide a fully nuanced discussion about the subtleties of the discussion.
Regardless, I would like to hear your thoughts. As a Christian or religious person how would you define atheism? As an atheist how would you define atheism?
 Brian Westley aptly pointed out that not every dictionary provides this particular definition. However, many that I consulted provided this definition or something akin to it; which is why I have used it as a starting point for our discussion. If you think this definition is incorrect, I would be interested to hear your thoughts or see what dictionary (and definition) you would suggest that I use.