Any one of a group of fats or fatlike substances, characterized by their insolubility in water and solubility in fat solvents such as alcohol, ether, and chloroform. The term is descriptive rather than a chemical name such as protein or carbohydrate. It includes true fats (esters of fatty acids and glycerol); lipoids (phospholipids, cerebrosides, waxes); and sterols (cholesterol, ergosterol).