lipid \lip"id\ n. [Gr. li`pos fat.] (Chem., Biochem.)
  
         Any of a variety of oily or greasy organic compounds found
         as
   major structural components of living cells; they
         are
   insoluble in water but soluble in organic solvents
         such as
   alcohol and ether, and include the common fats,
   cholesterol and
         other steroids, phospholipids,
  
         sphingolipids,
         waxes, and fatty acids;
         some of the
   lipids, together
         with proteins and carbohydrates, form an
   essential
         structural component of living cells, as in the
   cell
         walls and membranes. The term lipid refers to its
  
         solubility in nonpolar solvents, and has no significance
         with
   regard to chemical structure.

   Syn: lipide,
         lipoid.
        [WordNet 1.5]