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Definition of mullion

mullion

/ˈmʌl.jən/
mul · lion

Plural:mullions
•
Past Simple:mullioned
•
Past Participle:mullioned
•
Present Participle:mullioning
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mullion Lexical Profile

mullion Game Scores & Validity

• noun

1

A heavy vertical bar or structural member that separates adjacent window units, screens, or doors.

Example

"The ancient gothic cathedral featured towering stained-glass windows divided by intricately carved stone mullions."

Synonyms
View all synonyms for mullion

• verb

1

To provide or divide an architectural opening, such as a window, with vertical structural bars.

Example

"The architect decided to mullion the expansive glass facade to provide both aesthetic rhythm and essential structural support."

Word Nuance & Usage

Frequently confused in architecture with a 'muntin'; a mullion is the heavier vertical framing member that separates complete window units, whereas a muntin is the smaller inner strip separating individual panes of glass within a single sash.

• Rhymes for mullion

Word Origin & Etymology

Late 16th century: alteration of the earlier architectural term 'monial', possibly influenced by the French word 'moignon', meaning a stump or severed limb.

Usage Trend

Historical frequency of usage in published text.

180019102020

Cite this Entry


Wordmom. (2026). Definition of Mullion. In Wordmom Dictionary. Retrieved Nov 5, 2026, from https://wordmom.com/dictionary/mullion
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