1) How do you define knowledge?
2) What do you know?
I, personally, don't define "knowledge" differently from what the standard dictionary (Webster's et cetera) defines it.
Your second question is the basis of epistemology (the logic of knowing). There are works written by Austrian writers that touch on this, and go far more in depth than I will in this post, and some of them are very enlightening. Hoppe has written Economic Science and the Austrian Method in which he provides the praxeological basis for epistemology and argues that there exists knowledge that we can have without the need for experience (the notion that knowledge regarding reality can be only acquired through experience is the basis of empiricism, which Hoppe critiques; if you're interested in empiricism, I would recommend reading Popper), and that this knowledge can be acquired purely by the a priori fact that people argue. From this he deduces action and that action serves as the bridge that unites a priori epistemology to reality (while, I haven't read much apart from Hoppe concerning epistemology, I think he mentions that Kant was criticized for his rationalistic approach for being 'unrealistic').
So if you're looking to read up on epistemology, I would recommend the work above as it's a very short read at about 90 pages long and it is highly informative.
Hope this helps-
If I had a cake and ate it, it can be concluded that I do not have it anymore. HHH