1. <biochemistry> A pearly, fatlike steroid alcohol, C27H45OH, crystallizing in the form of leaflets or plates from dilute alcohol and found in animal fats and oils, in bile, blood, brain tissue, milk, yolk of egg, myelin sheaths of nerve fibres, the liver, kidneys and adrenal glands. It constitutes a large part of the most frequently occurring type of gallstones and occurs in atheroma of the arteries, in various cysts and in carcinomatous tissue. Most of the bodys cholesterol is synthesised in the liver, but some is absorbed from the diet. It is a precursor of bile acids and is important in the synthesis of steroid hormones. 2. <chemical> A commercial preparation of cholesterol is used as a pharmaceutic aid. Synonym: cholesterin. Origin: Gr. Stereos = solid (15 Jan 1998)