The Collaborative International Dictionary of English v.0.48:

Exacerbate \Ex*ac"er*bate\ ([e^]gz*[a^]s"[~e]r*b[=a]t; 277), v.
   t. [imp. & p. p. Exacerbated
   ([e^]gz*[a^]s"[~e]r*b[=a]`t[e^]d); p. pr. & vb. n.
   Exacerbating ([e^]gz*[a^]s"[~e]r*b[=a]`t[i^]ng).] [L.
   exacerbatus, p. p. of exacerbare; ex out (intens.) +
   acerbare. See Acerbate.]
   To render more violent or bitter; to irritate; to exasperate;
   to imbitter, as passions or disease. --Brougham.
   [1913 Webster]