any of several phosphatides found in nerve tissue, blood, milk, egg yolk, soybeans, corn, etc.: used in medicine, foods, cosmetics, etc. as a wetting, emulsifying, and penetrating agent
See lecithin in American Heritage Dictionary 4
(lĕsˈə-thĭn)
noun
Any of a group of phospholipids found in egg yolks and the plasma membrane of plant and animal cells, used as an emulsifier in a wide range of commercial products, including foods, cosmetics, paints, and plastics. Also called phosphatidylcholine.