mullioned definition
Mullion. A mullion is a vertical element that forms a division between units of a window, door, or screen, or is used decoratively.When dividing adjacent window units, its primary purpose is to provide structural support to an arch or lintel above the window opening.ts secondary purpose may be as a rigid support to the glazing of the window. When used to support glazing, they are teamed with horizontal supporting elements called transoms. In the commercial door industry, the term is also applied to a piece of hardware that divides the opening of a pair of doors.