layer a level of material, such as a type of rock or gas, that is different from the material above or below it, or a thin sheet of a substance 某种物质，比如岩石或气体，与它上面或下面的物质不同，或一种物质的薄片;层;涂层 the ozone layer 臭氧层 A thick layer of clay 一层厚厚的黏土 a thin layer of oil 一层薄薄的油膜 several layers of 好几层 There was a thin layer of oil on the surface of the water. 水面上有一层薄薄的油膜。