Definition of business 1a : a usually commercial or mercantile activity engaged in as a means of livelihood : trade, line in the restaurant business b : a commercial or sometimes an industrial enterprise also : such enterprises the business district Business is the practice of making one's living or making money by producing or buying and selling products (such as goods and services). It is also "any activity or enterprise entered into for profit." Having a business name does not separate the business entity from the owner.