The Collaborative International Dictionary of English v.0.48:
HDL \HDL\ ([=a]ch`d[=e]*[e^]l"), n. High density lipoprotein, a lipoprotein that transports cholesterol in the blood; high levels are thought to be associated with decreased risk of coronary heart disease and atherosclerosis; sometimes called good cholesterol. Contrasted with LDL. Syn: high-density lipoprotein. [WordNet 1.5]