noun (n)

• axis of a compound leaf or compound inflorescence(noun.plant)

  source: wordnet30
• the series of vertebrae forming the axis of the skeleton and protecting the spinal cord(noun.body)

  Synonym:
  back, backbone, spinal column, spine, vertebral column
  

  source: wordnet30
• The spine; the vertebral column.(noun)

  source: webster1913