Actually, the best definition of 'capital' is the one given to us by Karl Marx: capital is "the means of production".
Socialism is based on the belief that capital should not be privately owned.
Marx was not against the private ownership of all property. Personal possessions (the ends of production) were acceptable, but the means of production -- what Marx called "bourgeois property" -- had to be held publicly.
Benjamin Tucker summarized the Marxist distinction (which Tucker rejected) as follows:
To the individual can belong only the products to be consumed, not the means of producing them. A man may own his clothes and his food, but not the sewing-machine which makes his shirts or the spade which digs his potatoes. Product and capital are essentially different things; the former belongs to individuals, the latter to society.
-- "State Socialism and Anarchism: How far they agree, and wherein they differ."
Ideologically, then, the term 'capitalism' can be understood to mean the rejection of the Marxist thesis.
Ideological capitalism is the position that private individuals can legitimately own the means of production: sewing machines and spades, tractors and factories.
bkMarcus, Reluctant Capitalist
[bk]