(1):

(v. i.) To crumble into small particles; to turn to dust by natural decay; to lose form, or waste away, by a gradual separation of the component particles, without the presence of water; to crumble away.

(2):

Alt. of Mouldy

(3):

(v. t.) To turn to dust; to cause to crumble; to cause to waste away.

(4):

(n.) One who, or that which, molds or forms into shape; specifically (Founding), one skilled in the art of making molds for castings.