Use the word musty to describe an unclean, stale and possibly moldy smell. If something smells musty that means it’s probably been sitting in a damp corner without any air for a little too long.

Musty smells take time to develop: they’re caused by dampness and mold, and signal some amount of decay. You might also call the smell of a musty old basement rank or foul. But people also use musty to insult someone’s writing, or their ideas. A musty speech wouldn’t just be old-fashioned, it would be old in a bad way: rotten and boring.

Definitions of musty

adj covered with or smelling of mold

moldy, mouldy
lacking freshness, palatability, or showing deterioration from age

adj stale and unclean smelling

frowsty, fusty
ill-smelling, malodorous, malodourous, stinky, unpleasant-smelling
having an unpleasant smell

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