Source : Webster's Revised Unabridged Dictionary (1913)

Depreciate \De*pre"ci*ate\, v. t. [imp. & p. p. {Depreciated};
   p. pr. & vb. n. {Depreciating}.] [L. depretiatus,
   depreciatus, p. p. of depretiare, -ciare, to depreciate; de-
   + pretiare to prize, fr. pretium price. See {Price}.]
   To lessen in price or estimated value; to lower the worth of;
   to represent as of little value or claim to esteem; to
   undervalue. --Addison.

         Which . . . some over-severe phoilosophers may look
         upon fastidiously, or undervalue and depreciate.
                                                  --Cudworth.

         To prove that the Americans ought not to be free, we
         are obliged to depreciate the value of freedom itself.
                                                  --Burke.

   Syn: To decry; disparage; traduce; lower; detract; underrate.
        See {Decry}.

Depreciate \De*pre"ci*ate\, v. i.
   To fall in value; to become of less worth; to sink in
   estimation; as, a paper currency will depreciate, unless it
   is convertible into specie.

Source : WordNet®

depreciate
     v 1: belittle; "The teacher should not deprecate his student's
          efforts" [syn: {deprecate}]
     2: lower the value of something; "The Fed depreciated the
        dollar once again" [ant: {appreciate}]
     3: lose in value; "The dollar depreciated again" [syn: {undervalue},
         {devaluate}, {devalue}] [ant: {appreciate}]