An old house that has been shut up for years and that no fresh air has entered is an example of a house that would be described as musty.
Towels that are left in the washer too long after the cycle ends and that smell moldy and unclean are an example of towels that would be described as musty.
Origin of musty
- Alteration of obsolete moisty from moist
From American Heritage Dictionary of the English Language, 5th Edition