Source : Webster's Revised Unabridged Dictionary (1913)

Undervalue \Un`der*val"ue\, v. t.
   1. To value, rate, or estimate below the real worth; to
      depreciate.

   2. To esteem lightly; to treat as of little worth; to hold in
      mean estimation; to despise.

            In comparison of it I undervalued all ensigns of
            authority.                            --Atterbury.

            I write not this with the least intention to
            undervalue the other parts of poetry. --Dryden.

Undervalue \Un`der*val"ue\, n.
   A low rate or price; a price less than the real worth;
   undervaluation. --Milton.

Source : WordNet®

undervalue
     v 1: assign too low a value to; "Don't underestimate the value of
          this heirlooom-you may sell it at a good price" [syn: {underestimate}]
          [ant: {overvalue}, {overvalue}]
     2: esteem lightly
     3: lose in value; "The dollar depreciated again" [syn: {depreciate},
         {devaluate}, {devalue}] [ant: {appreciate}]