Good question. "Major expense" is a vague term and I'm actually not sure there is a formal definition. When I see "major expense," I envision an unexpected expense, or one that is unusual for a company. It depends how it is used in a sentence. Some examples:
- ABC Corp's cost of goods sold is a major expense since they manufacture everything in the US, unlike their competitors, who find lower costs when sourcing overseas. "Major expense" in this sentence is merely descriptive of a company's financial heatlh.
- ABC's settlement of FCC claims of false advertising be reflected a major expense in the coming fiscal quarter. Here, "major expense" signifies a large, one-time event.