adverb (r)

• not in a reasonable or intelligent manner(adv.all)

  Example:
  She reacted unreasonably when she learned she had failed.
  

  Antonym:
  reasonably, sanely, sensibly
  

  source: wordnet30
• to a degree that exceeds the bounds or reason or moderation(adv.all)

  Example:
  His prices are unreasonably high.
  

  Synonym:
  immoderately
  Antonym:
  fairly, jolly, middling, moderately, passably, pretty, reasonably, somewhat
  

  source: wordnet30