The Collaborative International Dictionary of English v.0.48:

Fusty \Fusty\, a. [Compar. Fustier; superl. Fustiest.] [See
   2d Fust.]
   1. Moldy; musty; ill-smelling; rank. "A fusty nut." "Fusty
      plebeians." --Shak.
      [1913 Webster]

   2. Moping. [Archaic]
      [1913 Webster]

            A melancholy, fusty humor.            --Pepys.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fusty
    adj 1: stale and unclean smelling [syn: fusty, musty,
           frowsty]
    2: old-fashioned and out of date [syn: fusty, standpat(a),
       unprogressive, nonprogressive]

Moby Thesaurus II by Grady Ward, 1.0:

114 Moby Thesaurus words for "fusty":
   archaic, back-number, bad, bad-smelling, banal, bewhiskered,
   blasted, blighted, blown, bromidic, bygone, close, common,
   commonplace, corny, crumbling, cut-and-dried, dated, despoiled,
   dilapidated, dirty, disheveled, dusty, fade, familiar, fecal,
   fetid, filthy, flyblown, foul, frowsty, frowsy, frowy, frowzy,
   fulsome, funky, gamy, gone to seed, graveolent, hackney, hackneyed,
   high, ill-smelling, maggoty, malodorous, mephitic, miasmal,
   miasmic, mildewed, mildewy, moldering, moldy, moss-grown,
   moth-eaten, musty, nidorous, noisome, noxious, odorous, offensive,
   old hat, olid, outdated, passe, platitudinous, putrid, rancid,
   rank, ravaged, reasty, reasy, reechy, reeking, reeky, repulsive,
   rotten, ruined, ruinous, rusty, set, slipshod, sloppy, slovenly,
   smellful, smelling, smelly, smutted, smutty, squalid, square,
   stale, stenchy, stereotyped, stinking, stock, strong, stuffy,
   sulfurous, threadbare, time-scarred, timeworn, trite, truistic,
   unkempt, unoriginal, vile, warmed-over, weevily, well-known,
   well-worn, worm-eaten, wormy, worn, worn thin