> Do you have a reference for that?
Google's dictionary in search defines it as “a commercial business”, dictionary.com defines it as “a number of persons united or incorporated for joint action, especially for business”;
Wiktionary has both a business definition “Any business, whether incorporated or not, that manufactures or sells products (also known as goods), or provides services as a commercial venture” and a law definition “An entity having legal personality, and thus able to own property and to sue and be sued in its own name; a corporation.”
FindLaw’s law dictionary gives “an association of persons for carrying on a commercial or industrial enterprise”
> It's not clear to me what a "business organization" means if it's not defined under law
It's a vague, broad category; the law mostly concerns itself with more specific categories.