The Collaborative International Dictionary of English v.0.48:

Aggravation \Ag`gra*va"tion\, n. [LL. aggravatio: cf. F.
   aggravation.]
   1. The act of aggravating, or making worse; -- used of evils,
      natural or moral; the act of increasing in severity or
      heinousness; something additional to a crime or wrong and
      enhancing its guilt or injurious consequences.
      [1913 Webster]

   2. Exaggerated representation.
      [1913 Webster]

            By a little aggravation of the features changed it
            into the Saracen's head.              --Addison.
      [1913 Webster]

   3. An extrinsic circumstance or accident which increases the
      guilt of a crime or the misery of a calamity.
      [1913 Webster]

   4. Provocation; irritation. [Colloq.] --Dickens.
      [1913 Webster]

WordNet (r) 3.0 (2006):

aggravation
    n 1: an exasperated feeling of annoyance [syn: aggravation,
         exasperation]
    2: unfriendly behavior that causes anger or resentment [syn:
       aggravation, irritation, provocation]
    3: action that makes a problem or a disease (or its symptoms)
       worse; "the aggravation of her condition resulted from lack
       of care" [syn: aggravation, exacerbation]