WordNet (r) 3.0 (2006):

demotion
    n 1: act of lowering in rank or position [ant: promotion]

Moby Thesaurus II by Grady Ward, 1.0:

84 Moby Thesaurus words for "demotion":
   banishment, blackballing, comedown, concavity, de-escalation,
   debasement, decadence, decadency, declension, declination, decline,
   deformation, defrocking, degeneracy, degenerateness, degeneration,
   degradation, depluming, deportation, depravation, depravedness,
   depreciation, depression, deprivation, derogation, descent,
   deterioration, detrusion, devolution, diminution, disbarment,
   disfellowship, displuming, downgrading, downtrend, downturn,
   downward mobility, downward trend, drop, ducking, dying, ebb,
   effeteness, exclusion, excommunication, exile, expatriation,
   extradition, fading, failing, failure, failure of nerve, fall,
   falling-off, fugitation, hauling down, hollowness, humbling,
   humiliation, involution, lapse, loss of tone, lowering, ostracism,
   ostracization, outlawing, outlawry, reduction, regression,
   relegation, retrocession, retrogradation, retrogression,
   rustication, sinking, slippage, slump, stripping, submergence,
   suspension, thrusting under, transportation, unfrocking, wane