the meaning of knowledge
Generally, the word "knowledge" is very inclusive because the AI community has discovered a vast array of knowledge representation forms, and every one of them is useful for some purpose or the other. Thus, the more important questions may not be what is and isn't knowledge, but given some knowledge, questions such as the following:
For what purposes can it be used? When is it applicable? Is it true? According to who? Under what circumstances? Who might find this knowledge useful? Is it expressed clearly enough? Are there other units of knowledge that may be useful in conjunction with this one? How long should we expect this knowledge to stay relevant? How might have this knowledge been acquired, and from where might we acquire more like it? What background might you need to make sense of it?
And so forth. The point, I suppose, is that like most words that point to complex ideas, understanding the word "knowledge" requires that we consider its many contexts of use, and the issues that show up in those contexts.