A process for discovering new knowledge about reality.
In my mind, I have found it useful to decompose science into roughly three domains. Each domain is an area of scientific discovery that has its own rules, assumptions, and process. While they have some overlap, reinforcing and informing each other, what makes each domain distinct is that it delves into and explores a territory that has (on the grand scale of things) very little overlap with the other domains.
The domains [1] are:
Phenomenological Science (AKA Phenomenology)
Analytical Science (AKA Analysis)
Empirical Science (AKA Empiricism [2])
[1]The domains are ordered, and their order is by time: i.e. phenomenology is the oldest domain of rigorous knowledge acquisition, and empiricism is the most recent.
[2]I expect that many, if not most, readers are entering this essay with the preconceived notion that only empiricism is "real" science.
What you think of when you think of 'science' is up to you. A part of the purpose of these essays is to try to get you to expand your understanding. I'm not promising it'll be easy, but it will be rewarding.
The reason why I have included Analysis and Phenomenology as branches of science is because they are both means of determining new knowledge about reality. Neither one is empirical (analysis does not rely on experimentation, and phenomenology is subject-dependent), so they cannot fit underneath that umbrella. Thus I have included them as siblings alongside empiricism. Don't mistake conceptual peerage with equivalency!