My accountant taught me this several years ago:
Business: Is the exchange of two pieces of paper, one of which MUST be a cheque.
And, of course, by cheque he meant a cheque, a deposit on a project, or the final payment on completion of a project.
But the definition also applies to public transit (you receive a paper transfer), buying a tub of iced-cream at the supermarket (they give you a receipt) and so on.
When I am swapping paper with a prospect, I'm not doing business with them.
So if Business is the exchange of two pieces of paper, one of which MUST be a cheque, then a Business Plan must be …?
A plan to do business.
A roadmap marking out how to get from wherever you are to the point where the prospect gives you a cheque.
A documented series of steps that follow in a logical manner, one leading to the other, where the final step is "Thank the Client for the cheque".