Do evolutionists distort the definition of science to somehow try an bolster the theory of evolution?

What does science actually mean? Is it no longer a form of epistemology which is based solely on what can be observed, tested and repeated in the present? I've heard it said by one of the members on here that science does not prove anything, and can only suggest testable explanations for the workings of nature, is this really true? I mean hasn't it been scientifically proven that blood goes around the body by way of a double circulation system or that myocardial infactions are caused by block coronary arteries? And if science doesn't actually prove anything what constitutes a scientific fact? Somebody please enlighten me as I am befuzzled to say the least.