This is one of the beliefs of the New atheists as outlined in the Wikipedia entry on New Atheism.
What do people mean by it and what are the examples?
In the Wikipedia page Dawkins is quoted as saying "It is completely unrealistic to claim, as Gould and many others do, that religion keeps itself away from science's turf, restricting itself to morals and values. A universe with a supernatural presence would be a fundamentally and qualitatively different kind of universe from one without. The difference is, inescapably, a scientific difference. Religions make existence claims, and this means scientific claims."
Since he said it, it seems sensible to take that as 'what people mean by it' don't you think rather than asking people who haven't used the phrase.