Mus"ty (?), a. [Compar. Mustier (?); superl. Mustiest.] [From L. mustum must; or perh. fr. E. moist. Cf. Must, n., Moist.] 1. Having the rank, pungent, offensive odor and taste which substances of organic origin acquire during warm, moist weather; foul or sour and fetid; moldy; as, musty corn; musty books. Harvey.

2. Spoiled by age; rank; stale.

The proverb is somewhat musty.

3. Dull; heavy; spiritless. "That he may not grow musty and unfit for conversation." Addison.