Source : Webster's Revised Unabridged Dictionary (1913)

Acerbate \A*cerb"ate\, v. t. [L. acerbatus, p. p. of acerbare,
   fr. acerbus.]
   To sour; to imbitter; to irritate.

Source : WordNet®

acerbate
     v 1: cause to be bitter or resentful; "These injustices
          embittered her even more" [syn: {embitter}, {envenom}]
     2: make sour or bitter