Longman Dictionary of Contemporary English
Wiktionary
n. 1 An umbrella term for any system of government-run health care. 2 (context US politics idiomatic English) A politically charged term used to contrast such systems with free market alternatives and emphasize the perceived link to socialism.
Wikipedia
Socialized medicine is a term used to describe and discuss systems of universal health care: medical and hospital care for all at a nominal cost by means of government regulation of health care and subsidies derived from taxation. Because of historically negative associations with socialism in American culture, the term is usually used pejoratively in American political discourse. The term was first widely used in the United States by advocates of the American Medical Association in opposition to President Harry S. Truman's 1947 health-care initiative.