A Latin meaning “for form”. It’s used in the sense of making or carrying out a task in a perfunctory manner or as a formality. In the design business, you will see it frequently used in relation to an invoice, as in providing one in advance to describe items or show how things should be presented. In general business, it can refer to balance sheets, etc.
Example: In an attempt to project the overall financial soundness of her small firm, the newly self-employed architect created a pro forma balance sheet to show her accountant the projected relative amount of money tied up in receivables, inventory, and equipment.