Broadly speaking, in American politics today the term is used to imply the increased scope, reach, and size of government, inevitably followed by an increase in taxes, It's not a textbook definition of socialism, but it boils down an aversion to the state controlling an increasing percentage of our personal wealth.
Whereas the alternative, conservatism promulgated by Republicans, implies the increased scope, reach and size of government (armies + war), inevitably followed by an increase in deficits (which "don't matter", but the redirected resources, even if only measured in terms of people employed, do make a difference in productive, rather than destructive, output).
