down 3 noun (usu. downs) a gently rolling hill : the gentle green contours of the downs. • ( the Downs) ridges of undulating chalk and limestone hills in southern England, with few trees and used...
To "lay down" is to "set something down", and it doesn't always mean set something down on the ground. However, there are other definitions. Take this sentense for instanse:
Henry layed down the job...