This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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n. The quality of being fusty

n. A fusty state or quality; moldiness; mustiness; an ill smell from moldiness.

n. The state or quality of being fusty; an ill smell from moldiness, or moldiness itself.

"First comes the hippy California dad – long hair, screechy kids, lots of sunny white light; then the awkward writer, all tweedy fustiness with a sepia tint; and finally the designer, dressed in requisite black geek glasses and cool blue tones."

fustily   

moldiness    mustiness