The term capitalist
has at least four distinct meanings: one economic, and three political. As a result, if you hear someone refer to themselves, you, or someone else as a "capitalist", you may very well not know what they mean
without further information.
Economically, a capitalist is any person who invests in a business or economic venture, taking on risk in expectation of future profit. A small business owner who starts up her business with her personal savings is a capitalist. So is anyone who owns stock, mutual funds, or pension funds; so is a venture capitalist or a prospector. All of these people invest wealth to provide capital for business, taking on the risk that their investments may or may not pay off. The provision of investment capital permits new businesses to start up, and established ones to expand.
In Marxist politics, a capitalist is a member of the capitalist class. The "capitalist class" is another term for the bourgeoisie, a supposedly exclusive sector of society which Marxists believe monopolizes the means of production and extracts surplus value from the proletariat by means of exploitation. Marxists believe that classes are disjoint; that every class has its natural ideology derived from its material conditions; and that the ideology of the capitalist class is "capitalism." By "capitalism" they mean a debased form of free market economics in which the right to profit from property is held superior to other rights.
In Cold War-era American politics, a capitalist is "not a communist." That is, a capitalist is a person who prefers an economic and political system broadly resembling that of the United States over one resembling that of the Soviet Union. The American claim during the Cold War was to represent the free market and personal freedom as opposed to the Soviet command economy and totalitarianism. In truth, the American economic system was not a free market: vast sectors fell (and still remain) under government command by way of regulation, subsidy, and the military-industrial complex. (Nor, for that matter, did Cold War America exemplify personal freedom, as was claimed. Being better than Stalin is not the same as being good.)
Finally, in the political terminology of some libertarians, a capitalist is a supporter of the free market. Libertarians disagree with both the Marxist and the Cold War American interpretation of the market and capitalism, seeing the freedoms to buy, sell, labor, and invest as corollaries of self-ownership and thus inseparable from individual liberty. Some libertarians — such as the present author — believe that the words "capitalism" and "capitalist" have already had quite enough meanings, thank you very much, and that libertarians had best find other words to refer to our positions if we are to be understood.
If you know any other distinct meanings of "capitalist", please let me know.