I was always struck by something attributed to Socrates or Plato, I honestly don't remember. But the statement was something along the lines of "if you truly know something, you cannot help but act according to it."
So it goes along in some ways with what the previous post says, when learning really happens behavior is affected. I would go so far as to say that even when thinking is truly changed that learning has also occurred.
Learning is change. Whenever there is a change in a person's behavior, learning has occurred. This applies to knowledge as well, because when you apply knowledge your behavior changes. When behavior does not change, learning has not really occurred.
Learning is collecting information and experiences, processing them, and being changed in the process: whether it is learning to see you or the world differently, understanding other people or history better, or even providing you with more questions than you started with.
Learning can be something tangible like tying a shoelace, but also intangible, like understanding that others have feelings.
Learning is a process that brings in all kinds of new information, and it should never stop. Age has no bearing on learning, except it seems easier to do (and remember) when you are younger. But the world is full of mysteries waiting to be uncovered, and whether you are the first to contemplate that mystery, or the millionth person to do so, it's not always about achieving a certain goal (getting a degree, for example), but sometimes it's about learning what is important to you and what your dreams are. Learning is like the flight of a kite: you never know where its winds will take you.
True learning is more than just memorizing information long enough to take a test or get through a class. As mentioned above learning takes place when we are able to use the information we learn in the way it is intended to be used.
Learning is not simply the way we learn but also what we do with that. Learning is the acquisition of new information, but it is also the ability to retain and retrieve that information in a meaningful way. True learning will empower us and making us stronger with mental knowledge that we can retrieve and use for our own purposes.
I don't think that the definition of learning itself has anything to do with how a person is taught. Different people may learn better through different forms of teaching, but learning is still defined the same way -- no matter if one learns through listening to a lecture or doing a lab.
Learning is simply the acquisition of new skills or new knowledge. A person has learned something if they are able to do something they could not do before (for example, typing) or if they have some piece of information they did not have before (knowing the Pythagorean Theorem).
I moved this to the "Teachers" category because it is one of those questions that educators upon which reflection is needed on an almost constant basis. To define it might move this question into a "Discussion" forum very quickly, as answers will differ. I think that learning involves some combination of guidance and instruction in the hope of establishing autonomy and independence. When one "learns" something, they understand the pattern of recognition in a problem to be able to complete or grasp a concept on their own. Guidance gives way to independence. The acquisition of new knowledge, understanding, application, or skills is something that is gained through instruction on some level. Yet, the element of "learning" something is when some aspect of independent comprehension can allow the learner to conduct the task on their own or with a more autonomous element whereby the instructor becomes more of a resource than the driving guide. I think that this is where learning is and where, to a great extent, my pedagogy lies.