Non-recurring, non-operating profit in a given fiscal year. Publicly-traded companies must include extraordinary gains (and extraordinary losses) on their annual and quarterly reports; they are usually explained separately so as not to detract from the companies' usual gains and losses. One of the most common extraordinary gains a company may report is the sale of a subsidiary or stake in another company for an amount greater than the asset value carried on the company's balance sheet.
Income from an unusual, infrequently occurring event or transaction. For example, a firm might sell a subsidiary at a price significantly higher than the value at which that subsidiary's assets are carried on the firm's balance sheet. An extraordinary gain is reported separately from regular income to emphasize the fact that it is nonrecurring.