It has a somewhat flexible meaning, but is usually used to refer to the partners (owners) of a business with an emphasis on the financial aspect of their owners

It has a somewhat flexible meaning, but is usually used to refer to the partners (owners) of a business with an emphasis on the financial aspect of their ownership. The ownership has to be significant; elementary shareholders don't qualify. It is also sometimes used more loosely of corporate officers, i.e. CxOs. The signature of a principal is often required in serious contracts. In other words, the defining attribute of a principal is his or her ability to represent the firm in a legally binding way with no limitations.