Life is the meaning of life. It's not anything outside of life and it's not even necessarily any particular content of life; or way of life. It's just life itself.
About the same time that Camus wrote The Stranger, he wrote a philosophical essay. (Which one might take as a theory that accompanies The Stranger, and perhaps explains it.) It's called The Myth Of Sisyphus.
Just to remind you, Sisyphus was a character in Greek mythology who was condemned by the Gods to a truly pointless task. He had to roll a rock up a mountain... and of course when he got to the top, it would roll down in it's own weight and he would have to do it again, and again, and again, and again. This is a kind of symbol of what Camus refers to, famously, as the absurd. He points out in his re-telling of the story of Sisyphus that one can't think of anything more absurd than a life time filled with futile labor.
Track Name: That Now
The absurd, which Camus says has overtaken modern sensibilities, which is really a kind of obsession with the way we see the world today, (The absurd) is really a metaphysical thesis. It's, to put it very bluntly, a confrontation. It's a confrontation between the rational human mind, the mind that deserves and demands justice, that expects the universe to be comprehensible; and what Camus calls (in a phrase that he borrows straight from The Stranger) an indifferent universe.
The truth is: the world doesn't care.
Track Name: And Forever
Without having a choice in the matter we project this sense on the universe. We expect the universe to fulfill our demands. We think, for example that evil should be punished. We think that goodness should be rewarded. This is the problem that goes all the way back to the early middle ages, often called the problem of evil. The obvious fact that virtue is not always rewarded. The obvious fact that the evil sometimes get away with what they do; has always been a deep problem for theological thinkers. But without even reference to religion, it's a problem for all of us.
The absurd is this recognition that we have a demand of the world and the world just doesn't care. Now, there's a sense in which we might say the absurd would cease to be a problem if we believe in God. Camus of course is an atheist. But the truth is that the absurd would exist even if there's a God. In fact the problem with evil, as it goes back through history, is very much a problem in the face of god. We have these expectations and the world doesn't seem to deliver.
At one point Camus says, even if there were a god, it wouldn't matter.
Track Name: Meant Nothing
In The Stranger it's often said, and Mersault says, that it's death that makes life absurd but the idea that death leads to the absurd gives rise to another consideration too. That there's a sense in which we expect our lives to add up to something. As Ecclesiastes in the old testatement tells us, this is the vanity of vanities. It doesn't. What Sisyphus and Ecclesiastes both give us, is a picture of life where we have all of our aspirations and ambitions, our joys and our achievements but ultimately in the end... it amounts to nothing.
That's the absurd.
Track Name: To Me
There's another sense in which Camus takes us to his target...the whole of the scientific world view, the idea of objectivity. The thesis basically is that it's only life, only one's personal experience that really counts.