Holliday got it right; atheism is a broad term that blankets any person who does not include any god in their beliefs. Although we may believe anything, even something completely and utterly irrational, so long as those beliefs do not include god, it's still atheism.
I believe it's better to define atheism not as itself a belief, but more of a "who cares"; there's more important things to worry about than whether or not there's a God, such as what's on TV, or what I might eat for dinner tonight. There cannot be an atheist without a theist, for if we have one and not the other, it's as strange as noticing that there's oxygen everywhere; we don't often think about the moments when there isn't. Although it may be obvious that there's a stark contrast between theist and atheists today, there was a time when atheism was downright impossible to imagine, and I believe there will be a time in the future where upon learning that most people of today believed in mythological creatures, the future-people will draw long and odd glances.
However, I must disagree with you on the point of life; if the point of life is to change life, or to accomplish some unthinkable goal, then life is pointless, for our time here is limited, and we'll never be able to accomplish, and surely not alone, whatever end-game life has in store for us (I imagine that moment isn't going to be fun), nor would we even be around to see it. If, on the other hand, we may view life solely to appease our sense of happiness, then the one who spends more of his time here happy is ultimately the winner in his own end. If we're under the belief that nothing happens once we die, it is imperative to accomplish such a task while we're still aware we can accomplish it.
With this in mind, the person who believes in God and is also happy, is doing better than the person who does not believe in God and is unhappy; however, if it is true that God brings happiness, there would be no atheists. So what brings happiness? Is it the truth?--no, the truth, as we've examined in the various "smarter" folk on this planet, often makes people unhappier than those who are blissfully ignorant (and with good reason; who could be happy knowing what governments are doing to this world?) If the truth does not bring happiness, then why do we seek it? Perhaps, then, we are not naturally inclined to be happy, but naturally inclined to survive; it is at this point there is a disconnect between what makes an organism human and what makes him like any other creature on the planet, for if we are to assume human beings are just clusters of smaller organisms that occur over a stretch of time, powered by whatever other organisms it will consume, then surely life appears to not have a point; after all, the grass does not grow because it wants to, it is simply programmed to do so.
So if we look at life this way, through a cold and logical lens, we will never find a reason for it; it just is; it's not until we use what no other animal has that we can find meaning in it, for we are the only creatures who have the capacity to apply meaning. But this, as you say, is where atheism ends; atheism applies to just one, singled-out idea. I'm not sure if there is a word for belief in nothing; I believe
nihilism would be appropriate.