Stripe says "the singularity" has begun

And if you say "I don't see that", then the response is going to be either "the future is already here, it's not just evenly distributed", or else that you just don't understand what you're seeing. That is, this is a claim that is impossible to refute, since any evidence against it gets dismissed out of hand.

The other possible meaning is that we have reached a point where AI is self-improving, and is improving itself at a faster rate than humans could, and the rate of improvement is itself increasing. Proving that (or even disproving it) would take some agreed-upon way of measuring how good AI is at any point in time. So again, a claim that is impossible to refute, since you cannot gather meaningful data.

If it doesn't mean either of those things, then it is just a vague, meaningless claim. That also is impossible to refute, since the claim isn't precise enough to tell what it means.