mullion.

a vertical or horizontal member dividing adjacent panes or sections of a window

Use it for

Words that belong together

• stone mullion
• slender mullions
• mullioned window

On the page

Stone mullions divided the window into three narrow lights.

Rain ran down the metal mullion.

One broken mullion left the glass unsupported.

Usage notes

Primary curation section: Architecture. A mullion divides window units; a muntin more specifically holds individual small panes. Terminology varies with building practice. Plural: mullions. Related adjective: mullioned.