The Collaborative International Dictionary of English v.0.48:

Comedown \Come"down`\, n.
   A downfall; an humiliation. [Colloq.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

comedown
    n 1: decline to a lower status or level

Moby Thesaurus II by Grady Ward, 1.0:

151 Moby Thesaurus words for "comedown":
   abasement, anticlimax, backset, bafflement, balk, bathos,
   belittling, betrayed hope, blasted expectation, blighted hope,
   blow, breakdown, buffet, cascade, cataract, check, chute, collapse,
   contempt, crash, cropper, cruel disappointment, dash, dashed hope,
   debacle, debasement, decadence, decadency, declension, declination,
   decline, decrial, defeat, deflation, defluxion, deformation,
   degeneracy, degenerateness, degeneration, degradation, demotion,
   depravation, depravedness, depreciation, derogation, descending,
   descension, descent, deterioration, detraction, devolution,
   disappointment, disapproval, discomfiture, discrediting, disgrace,
   disillusionment, disparagement, dissatisfaction, down, downbend,
   downcome, downcurve, downfall, downflow, downgrade, downpour,
   downrush, downtrend, downturn, downward mobility, downward trend,
   drop, dropping, dump, dying, ebb, effeteness, embarrassment,
   fading, failing, failure, failure of nerve, faint praise, fall,
   fallen countenance, falling, falling-off, fiasco, fizzle, foiling,
   forlorn hope, frustration, gravitation, hangdog look,
   hope deferred, humbled pride, humiliation, inclination, indignity,
   involution, knocking, lapse, letdown, loss of tone,
   lukewarm support, minimizing, mirage, mortification, nose dive,
   plummeting, pounce, pratfall, put-down, putting down, rapids,
   regression, retrocession, retrogradation, retrogression, reversal,
   reverse, reverse of fortune, ruin, self-abasement, self-abnegation,
   self-diminishment, setback, setdown, severe check, shame,
   shamefacedness, shamefastness, slighting, slippage, slump, smash,
   sore disappointment, sour grapes, stoop, stumble, swoop, tailspin,
   tantalization, tease, throwback, tumble, undoing, wane, waterfall,
   wreck