The Collaborative International Dictionary of English v.0.48:

Debase \De*base"\, v. t. [imp. & p. p. Debased; p. pr. & vb.
   n. Debasing.] [Pref. de- + base. See Base, a., and cf.
   Abase.]
   To reduce from a higher to a lower state or grade of worth,
   dignity, purity, station, etc.; to degrade; to lower; to
   deteriorate; to abase; as, to debase the character by crime;
   to debase the mind by frivolity; to debase style by vulgar
   words.
   [1913 Webster]

         The coin which was adulterated and debased. --Hale.
   [1913 Webster]

         It is a kind of taking God's name in vain to debase
         religion with such frivolous disputes.   --Hooker.
   [1913 Webster]

         And to debase the sons, exalts the sires. --Pope.

   Syn: To abase; degrade. See Abase.
        [1913 Webster]

WordNet (r) 3.0 (2006):

debase
    v 1: corrupt morally or by intemperance or sensuality; "debauch
         the young people with wine and women"; "Socrates was
         accused of corrupting young men"; "Do school counselors
         subvert young children?"; "corrupt the morals" [syn:
         corrupt, pervert, subvert, demoralize,
         demoralise, debauch, debase, profane, vitiate,
         deprave, misdirect]
    2: lower in value by increasing the base-metal content [syn:
       debase, alloy]
    3: corrupt, debase, or make impure by adding a foreign or
       inferior substance; often by replacing valuable ingredients
       with inferior ones; "adulterate liquor" [syn: load,
       adulterate, stretch, dilute, debase]

Moby Thesaurus II by Grady Ward, 1.0:

154 Moby Thesaurus words for "debase":
   abase, abash, abuse, adulterate, alloy, bastardize, bear down,
   befoul, belittle, bring down, bring into discredit, bring low,
   bring shame upon, brutalize, bump, bust, canker, cast down,
   cast reproach upon, cheapen, coarsen, commercialize, confound,
   contaminate, convert, corrupt, couch, cripple, crush, cry down,
   cut, damage, debauch, debilitate, decry, defalcate, defile,
   deflower, defrock, degenerate, degrade, demean, demoralize, demote,
   denaturalize, denature, deplume, deprave, deprecate, depreciate,
   depress, derogate from, desecrate, despoil, detract from, detrude,
   devalue, dilute, diminish, disable, disapprove of, discredit,
   disgrace, disgrade, dishonor, disparage, displume, distort, divert,
   doctor, doctor up, downbear, downgrade, dump, dump on, embezzle,
   enfeeble, fortify, foul, harm, haul down, hold in contempt, humble,
   humiliate, impair, impute shame to, indent, infect, injure, knock,
   lace, let down, load, lower, make little of, maladminister, mar,
   minimize, misapply, misappropriate, misemploy, mishandle,
   mismanage, misuse, peculate, pervert, pilfer, pillory, poison,
   pollute, press down, profane, prostitute, pull down, push down,
   put down, put to shame, ravage, ravish, reduce,
   reflect discredit upon, reproach, rot, run down, sap, set down,
   shame, sink, slight, sophisticate, speak ill of, spike, spoil,
   stain, strip of rank, submit to indignity, taint, take down,
   tamper with, thrust down, trip up, twist, ulcerate, undermine,
   unfrock, violate, vitiate, vulgarize, warp, water, water down,
   weaken, weight, worsen