1. vertical bars or strips of stone, wood, or metal that divide the panes of a window
Usage: architecture

Examples

• The Gothic cathedral featured tall windows with ornate stone mullions.
• The carpenter installed wooden mullions to divide the large window into smaller panes.
• Traditional colonial houses often have windows with white-painted mullions.
• The architect designed the facade with narrow mullions between each glass panel.
• Restoration work included repairing the damaged mullions on the historic building.
• Modern windows sometimes use decorative mullions that don’t actually separate the glass.