English to English

noun (n)

• lack of normal muscular tension or tonus(noun.state)

  Synonym:
  amyotonia, atonia, atonicity
  Antonym:
  tone, tonicity, tonus
  

  source: wordnet30
• Want of tone; weakness of the system, or of any organ, especially of such as are contractile.(noun)

  source: webster1913