Source : Webster's Revised Unabridged Dictionary (1913)

Abatement \A*bate"ment\ (-ment), n. [OF. abatement, F.
   abattement.]
   1. The act of abating, or the state of being abated; a
      lessening, diminution, or reduction; removal or putting an
      end to; as, the abatement of a nuisance is the suppression
      thereof.

   2. The amount abated; that which is taken away by way of
      reduction; deduction; decrease; a rebate or discount
      allowed.

   3. (Her.) A mark of dishonor on an escutcheon.

   4. (Law) The entry of a stranger, without right, into a
      freehold after the death of the last possessor, before the
      heir or devisee. --Blackstone.

   {Defense in abatement}, {Plea in abatement}, (Law), plea to
      the effect that from some formal defect (e.g. misnomer,
      want of jurisdiction) the proceedings should be abated.

Source : WordNet®

abatement
     n 1: an interruption in the intensity or amount of something
          [syn: {suspension}, {respite}, {reprieve}, {hiatus}]
     2: the act of abating; "laws enforcing noise abatement"