The Collaborative International Dictionary of English v.0.48:

Degrade \De*grade"\, v. t. [imp. & p. p. Degraded; p. pr. &
   vb. n. Degrading.] [F. d['e]grader, LL. degradare, fr. L.
   de- + gradus step, degree. See Grade, and cf. Degree.]
   1. To reduce from a higher to a lower rank or degree; to
      lower in rank; to deprive of office or dignity; to strip
      of honors; as, to degrade a nobleman, or a general
      officer.
      [1913 Webster]

            Prynne was sentenced by the Star Chamber Court to be
            degraded from the bar.                --Palfrey.
      [1913 Webster]

   2. To reduce in estimation, character, or reputation; to
      lessen the value of; to lower the physical, moral, or
      intellectual character of; to debase; to bring shame or
      contempt upon; to disgrace; as, vice degrades a man.
      [1913 Webster]

            O miserable mankind, to what fall
            Degraded, to what wretched state reserved! --Milton.
      [1913 Webster]

            Yet time ennobles or degrades each line. --Pope.
      [1913 Webster]

            Her pride . . . struggled hard against this
            degrading passion.                    --Macaulay.
      [1913 Webster]

   3. (Geol.) To reduce in altitude or magnitude, as hills and
      mountains; to wear down.

   Syn: To abase; demean; lower; reduce. See Abase.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Degrade \De*grade"\, v. i. (Biol.)
   To degenerate; to pass from a higher to a lower type of
   structure; as, a family of plants or animals degrades through
   this or that genus or group of genera.
   [1913 Webster]

WordNet (r) 3.0 (2006):

degrade
    v 1: reduce the level of land, as by erosion [ant: aggrade]
    2: reduce in worth or character, usually verbally; "She tends to
       put down younger women colleagues"; "His critics took him
       down after the lecture" [syn: take down, degrade,
       disgrace, demean, put down]
    3: lower the grade of something; reduce its worth [syn:
       degrade, cheapen]

Moby Thesaurus II by Grady Ward, 1.0:

143 Moby Thesaurus words for "degrade":
   abase, abash, adulterate, alloy, belittle, boot, bounce, break,
   bring down, bring into discredit, bring low, bring shame upon,
   bump, bust, can, canker, cashier, cast down, cast reproach upon,
   cheapen, coarsen, confound, contaminate, corrupt, crush, cry down,
   debase, debauch, decry, defile, deflower, defrock, degenerate,
   demean, demerit, demote, denature, deplume, depose, deprave,
   deprecate, depreciate, deprive, derogate, derogate from, desecrate,
   despoil, detract, detract from, devalue, dilute, diminish,
   disapprove of, disbar, discharge, discredit, disemploy,
   disenfranchise, disfranchise, disgrace, disgrade, dishonor,
   dismiss, disparage, displace, displume, distort, downgrade,
   drum out, dump, dump on, expel, fire, furlough, give the ax,
   give the gate, hold in contempt, humble, humiliate,
   impute shame to, infect, kick, kick upstairs, knock, lay off,
   lessen, let go, let out, lower, make little of, make redundant,
   minimize, misuse, mortify, pension off, pervert, pillory, poison,
   pollute, prostitute, put down, put to shame, ravage, ravish,
   read out of, reduce, reflect discredit upon, release, remove,
   replace, reproach, retire, rule out, run down, sack,
   separate forcibly, set down, shame, sink, slight, speak ill of,
   strip, strip of rank, submit to indignity, superannuate, surplus,
   suspend, taint, take down, thin, trip up, turn off, turn out,
   twist, ulcerate, unfrock, unseat, violate, vitiate, vulgarize,
   warp, water down, weaken