mul·​lion ˈməl-yən How to pronounce mullion (audio)
: 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 Not because of the large window profiles and reduced mullions on the upper decks that enhance the view, or the extended flydeck with a large Jacuzzi for soaks and cocktails. Julia Zaltzman, Robb Report, 3 Nov. 2023 Daniel and Feldman were so exacting about the symmetry between the upper windows and the doors below that the couple made sure that when the sliding doors were closed, the edges lined up with the mullions above. Caron Golden, San Diego Union-Tribune, 22 Apr. 2023 Architectural details include eyebrow dormer windows, two-story columns and spiderweb mullion windows, according to Ms. Seery. Sarah Paynter, WSJ, 10 Mar. 2022 Then, spread glue in the back rail mortises and on the mullion tenons. Darren Orf, Popular Mechanics, 8 Aug. 2020 Mark the locations of the mullion mortises in the back rails and rout them with a 3/8-in. Darren Orf, Popular Mechanics, 8 Aug. 2020 Mies made the mullions in the same I-beam shape as the steel structure inside the building. Michael Kimmelman, New York Times, 29 Apr. 2020 Nonetheless, Hancock’s board, determined to avoid future embarrassments, decided that as the building was repaired, each large sheet of glass should be replaced by three smaller panels, separated by mullions. Fred A. Bernstein, New York Times, 4 Mar. 2020 The paneled wood walls and lack of trim are modern touches, as is the floor-to-ceiling window, but the small panes and mullions are traditional. Mimi Read, House Beautiful, 2 Jan. 2013

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'mullion.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


probably alteration of monial mullion

First Known Use

1567, in the meaning defined above

Time Traveler
The first known use of mullion was in 1567

Dictionary Entries Near mullion

Cite this Entry

“Mullion.” Dictionary, Merriam-Webster, Accessed 29 May. 2024.

Kids Definition


mul·​lion ˈməl-yən How to pronounce mullion (audio)
: a slender upright bar which separates sections of windows, doors, or screens
mullion verb

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