If you read beyond the first sentence of that definition, you get a point I would be inclined to bring up.
"A more comprehensive definition of socialism is an economic system that directly maximizes use-values as opposed to exchange-values and has transcended commodity production and wage labour, along with a corresponding set of social and economic relations, including the organization of economic institutions, the method of resource allocation and post-monetary calculation based on some physical magnitude;[4] often implying a method of compensation based on individual merit, the amount of labour expended or individual contribution."
First of all, I can't believe that's one sentence. Secondly, a free market economy, and a socialist economy are not mutually exclusive. Just as a capitalist economy and a free market economy are not necessarily one and the same. One could draw attention at capitalism's tendency to create monopolies and thus abolishing the concept of a free market in it's wake (just one example). This is all covered in Capital Volume 1, which anyone with a fleeting interest in economics should have read.