NOUN (3)

1. the amount by which something increases;

2. the statement of a theme in notes of greater duration (usually twice the length of the original);

3. the act of augmenting;

The Collaborative International Dictionary of English v.0.48:

Augmentation \Aug`men*ta"tion\, n. [LL. augmentatio: cf. F.
   augmentation.]
   1. The act or process of augmenting, or making larger, by
      addition, expansion, or dilation; increase.
      [1913 Webster]

   2. The state of being augmented; enlargement.
      [1913 Webster]

   3. The thing added by way of enlargement.
      [1913 Webster]

   4. (Her.) A additional charge to a coat of arms, given as a
      mark of honor. --Cussans.
      [1913 Webster]

   5. (Med.) The stage of a disease in which the symptoms go on
      increasing. --Dunglison.
      [1913 Webster]

   6. (Mus.) In counterpoint and fugue, a repetition of the
      subject in tones of twice the original length.
      [1913 Webster]

   Augmentation court (Eng. Hist.), a court erected by Stat.
      27 Hen. VIII., to augment the revenues of the crown by the
      suppression of monasteries. It was long ago dissolved.
      --Encyc. Brit.
      [1913 Webster]

   Syn: Increase; enlargement; growth; extension; accession;
        addition.
        [1913 Webster]

WordNet (r) 3.0 (2006):

augmentation
    n 1: the amount by which something increases
    2: the statement of a theme in notes of greater duration
       (usually twice the length of the original) [ant:
       diminution]
    3: the act of augmenting

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "augmentation":
   accession, accretion, adjunct, annex, attachment, bonus, boot,
   complement, enhancement, enrichment, extra, fixture, increase,
   increment, plus, raise, reinforcement, rise



Bouvier's Law Dictionary, Revised 6th Ed (1856):

AUGMENTATION, old English law. The name of a court erected by Henry VIII.,
which was invested with the power of determining suits and controversies
relating to monasteries and abbey lands.