If the wine has a stale or moldy odor or taste, it's referred to as musty. A number of things can cause this, including moldy grapes, a bad cork, or poorly cleaned fermenting tanks or barrels. You usually know a wine is musty the second it's uncorked, because a rather rank odor shoots straight up your nose. A mild case of mustiness will sometimes dissipate if you air the wine for a while, but more often than not you're better off pouring the wine down the sink. FYI, the adjective "musty" has nothing to do with "must," which is a winemaker's term for unfermented grape juice