: a slender vertical member that forms a division between units of a window, door, or screen or is used decoratively
mullion
transitive verb
Examples of mullion in a Sentence
Recent Examples on the Web
Forth Bagley, the lead architect on the project, used white glazed tiles for the vertical mullions of the structure, a nod to a local craft tradition.
—
Nathalie Nietzsche-Knappe, Architectural Digest, 7 Apr. 2026
The Seagram Building's 27.5-foot structural bays and standardized bronze mullions could be manufactured off-site and assembled into countless configurations.
—Dr. Taha Kass-Hout, Forbes.com, 15 Sep. 2025
Expansive glass walls, subdivided into rectangles by steel mullions, offer tantalizing glimpses into the daily and work life of its occupants.
—The Editors, JSTOR Daily, 8 Apr. 2025
One of the most in-demand services WTS offers is window mullion and frame repair.
—Kyle J. Russell, USA TODAY, 6 Mar. 2025
Photo: Tim Street-Porter The window treatments have wavy valences and stripped mullions in some places.
—Tim Street-Porter, Curbed, 3 Mar. 2025
The full-height glazing with narrow mullions creates incredible vistas.
—Julia Zaltzman, Robb Report, 3 Feb. 2025
There are endless options from pane styles to number of mullions.
—Cameron Beall, Southern Living, 12 Aug. 2024
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Nathalie Nietzsche-Knappe, Architectural Digest, 7 Apr. 2026
The Seagram Building's 27.5-foot structural bays and standardized bronze mullions could be manufactured off-site and assembled into countless configurations.
—Dr. Taha Kass-Hout, Forbes.com, 15 Sep. 2025
Expansive glass walls, subdivided into rectangles by steel mullions, offer tantalizing glimpses into the daily and work life of its occupants.
—The Editors, JSTOR Daily, 8 Apr. 2025
One of the most in-demand services WTS offers is window mullion and frame repair.
—Kyle J. Russell, USA TODAY, 6 Mar. 2025
Photo: Tim Street-Porter The window treatments have wavy valences and stripped mullions in some places.
—Tim Street-Porter, Curbed, 3 Mar. 2025
The full-height glazing with narrow mullions creates incredible vistas.
—Julia Zaltzman, Robb Report, 3 Feb. 2025
There are endless options from pane styles to number of mullions.
—Cameron Beall, Southern Living, 12 Aug. 2024
Cite this Entry
“Mullion.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mullion. Accessed 21 Apr. 2026.
Copy CitationKids Definition
mullion
noun
mul·lion
ˈməl-yən 
: a slender upright bar which separates sections of windows, doors, or screens
mullion
verb
Love words? Need even more definitions?
Merriam-Webster unabridged
