The broad definition I use is this:
A resource is anything that's used to produce goods.
(I treat the terms resource, factor of production, means of production, and input as interchangeable.)
I neatly divide all resources into three categories:
So, labor refers to human beings (or more correctly, the services thereof). Examples: (the services of) a farmer, a lawyer, or a janitor.
Natural resources are any non-human resources that are not produced by human beings. Examples: A piece of land, an oil field, a coal mine, a lake.
Capital or capital goods are any non-human resources that are produced by human beings. Examples: A factory building, a copy of Microsoft Word installed on an office computer, a shipping container, a restaurant kitchen knife.
Classically, Land took the place of Natural resources, but these days it is probably better to speak of the broader term Natural resources.
The above is an example of a model.
The real world is extremely complex and so to understand it better, economists make simplifications that they call models.
A successful model succeeds in helping us understand and explain the world better. Hopefully, the above model is at least somewhat successful.
We should however be keenly aware that the above model is not perfect and certainly not realistic. Instead, it is merely an aid to our understanding of the world.
For example, in the real world, "resources" cannot be so easily divided into the above three categories. Example: Is a flock of sheep categorized under Capital or Natural resources? It turns out that by convention, we categorize a flock of sheep under Capital, the justification being that a flock of sheep must be bred by human beings. One could however quibble with this justification.
And, as you mention, some economists might insist that we include as a fourth and distinct resource Entrepreneurship. There is merit to this view, but for simplicity, in my above model, I simply subsume this under Labour.