The Collaborative International Dictionary of English v.0.48:

LDL \LDL\ ([e^]l`d[=e]*[e^]l/") n. [acronym from Low-Density
   Lipoprotein.] (Med., Biochem.)
   Low-density lipoprotein, a lipoprotein that transports
   cholesterol in the blood; high levels are thought to be
   associated with increased risk of coronary heart disease and
   atherosclerosis; sometimes called informally bad
   cholesterol.

   Syn: low-density lipoprotein.
        [WordNet 1.5]