WordNet (r) 3.0 (2006):

high-density lipoprotein
    n 1: a lipoprotein that transports cholesterol in the blood;
         composed of a high proportion of protein and relatively
         little cholesterol; high levels are thought to be
         associated with decreased risk of coronary heart disease
         and atherosclerosis [syn: high-density lipoprotein,
         HDL, alpha-lipoprotein]