WordNet (r) 3.0 (2006):

Medicare
    n 1: health care for the aged; a federally administered system
         of health insurance available to persons aged 65 and over

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "Medicare":
   ADC, Medicaid, aerospace medicine, biomedicine, clinical medicine,
   comparative medicine, constitutional medicine,
   cradle-to-grave security, dosimetric medicine,
   experimental medicine, guaranteed annual income, guaranteed income,
   health insurance, internal medicine, leechcraft, leechdom,
   legal medicine, materia medica, medical jurisprudence, medicine,
   military medicine, naval medicine, neo-Hippocratic medicine,
   old-age assistance, physic, physical medicine,
   preclinical medicine, preventive medicine, psychosomatic medicine,
   public assistance, public health medicine, relief,
   sickness insurance, social insurance, social security,
   social welfare, socialized medicine, space medicine,
   state medicine, therapy, tropical medicine,
   unemployment compensation, unemployment insurance,
   veterinary medicine, welfare, welfare capitalism, welfare payments,
   welfare state, welfare statism, welfarism, womb-to-tomb security