Larry Moran points us to the following video on what science is and why pseudoscience is not to be taught or accepted without serious evidence (which makes it science). My only comment to add is that emotional appeals are information and evidence, but they are information and evidence about the speaker, and not about the things that are being spoken of.
There are a number of people trying to give short definitions of science on the blogs right now (see here). I have a one line definition that I think captures everything I want it to, and nothing else:
Science is the process of saying as much as one can about measurable (empirical) phenomena in as simple a model as possible. Or more simply, science says as much as it can in as short a sentence as possible.