Layer

1. One who, or that which, lays.
2. That which is laid; a stratum; a bed; one thickness, course, or fold laid over another; as, a layer of clay or of sand in the earth; a layer of bricks, or of plaster; the layers of an onion.
3. A shoot or twig of a plant, not detached from the stock, laid under ground for growth or propagation.
4. An artificial oyster bed.