1. Lecithin is an emulsifier used to reduce the viscosity, or thickness of chocolate. The thinning of chocolate slightly reduces the amount of cocoa butter required to produce the correct texture in the manufacturing process.
2. 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.