ACM interviews Kurzweil.

The "singularity" is a metaphor borrowed from physics, really referring to the event horizon. We can't easily see beyond the event horizon around the black hole in physics. And here with regard to this historical singularity, we can't easily see beyond that event horizon, because it's so profoundly transformative. We will literally multiple the intelligence of our civilization by merging with, and supplementing our biological intelligence, with this profoundly more capable nonbiological intelligence by a factor of billions, ultimately trillions. And that will dramatically change the nature of human civilization. That in a nutshell is what the singularity is all about.