I have a feeling I posted this before, but perhaps it wasn't here.
It is the definition of Capitalism from E.K. Hunt's text History of Economic Thought 2e.
Capitalism is characterized by four sets of institutional and behavioral arrangements: market-oriented commodity production; private ownership of the means of production; a large segment of the population that cannot exist unless it sells its labor power in the market; and individualistic, acquisitive, maximizing behavior by most individuals within the economic system.
Commodity production exists when products are created by producers who have no immediate personal concern for the use value of the product but are interested only in its exchange value. Thus commodity production is not a direct means of satisfying needs. Rather, it is a means of acquiring money by exchanging the product for money, which in turn may be used to acquire products desired for their use value. Under such conditions the products of human labor are commodities, and the society is described as a commodity-producing society. ...Each individual depends on the impersonal forces of the market--of buying and selling or demand and supply--for the satisfaction of needs.
...Private ownership of the means of production...means that society grants to private persons the right to dictate how the raw materials, tools, machinery, and buildings necessary for production can be used...But very early in the evolution of capitalism things developed very differently. In fact...most producers do not own the means necessary to carry on their productive activity. Ownership came to be concentrated in the hands of a small segment of society--the capitalists. An owner-capitalist needed to play no direct role in the actual process of production in order to control it; ownership itself granted control. And it was this ownership that permitted the capitalist to appropriate the social surplus. Thus ownership of the means of production is the feature of capitalism that bestows power on the capitalist class by which it controls the social surplus and thereby establishes itself as the dominant social class.
This domination, of course, implies the third defining feature of capitalism--the existence of a large working class that has no control over the means necessary to carry out their productive activity...The typical worker enters the market owning or controlling only one thing--the capacity to work, that is, his or her labor power. In order to engage in productive activity, the person must sell his or her labor power to a capitalist. In return the person receives a wage and produces commodities that belong to the capitalist. Thus...capitalism turns human productive power itself into a commodity...and generates a set of conditions in which the majority of people cannot live unless they are able to sell their commodity, labor power, to a capitalist for a wage. With the wage, they are able to buy back from the capitalists only a portion of the commodities that they themselves have produced. The remainder of the commodities that they produce constitutes the social surplus and is retained and controlled by the capitalist class.
The fourth and final defining feature of capitalism is that most people are motivated by individualistic, acquisitive, maximizing behavior. ...First, in order to assure an adequate supply of labor and to facilitate the control of workers, it is necessary that working people produce commodities whose value is far in excess of the value of the commodities that they consume. In the earliest period of capitalism this was accomplished in two ways. First, workers were paid such low wages that they and their families were kept on the verge of extreme mental deprivation and insecurity. The only apparent way of decreasing this deprivation and insecurity was to work longer and harder in order to obtain a more adequate wage and to avoid being forced to join the large army of unemployed workers, which has been an ever present social phenomenon in the capitalist system.
From there, he goes on to discuss psychological effects of "consumerism" and the competition amongst capitalists. But it shows how difficult it is to construct a proper definition of capitalism.