Mullion
“MULL-yun”
The structural post between two separate window units joined side by side.
What it means for you
Not the same as a muntin (the thin grille bars). A mullion is load-bearing — it's what holds a two- or three-window combination together, and a factory-mulled unit is sturdier than one joined on-site.
Where you'll see it
In multi-window combinations and “mulled unit” notes on a quote.
Related terms
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