[1] : The Collaborative International Dictionary of English v.0.48

rachis \ra"chis\ r=a"ki^s, n.; pl. e. rachises
   r=a"ki^se^z, l. rachides ra^k"i^d=ez.
   nl., fr. gr. "ra`chis, -ios. written also rhachis.
   1. anat. the spine; the vertebral column.
      1913 webster

   2. bot.  zool. same as rhachis.
      1913 webster
see also:
rachises rachides rhachis rhachis 

[2] : WordNet (r) 2.0

rachis
     n 1: axis of a compound leaf or compound inflorescence
     2: the series of vertebrae forming the axis of the skeleton and
        protecting the spinal cord; "the fall broke his back"
        syn: spinal column, vertebral column, spine, backbone,
         back
     also: rhachises pl
see also:
spinal column vertebral column spine backbone back rhachises 

Rachis >> R Words
Rachis, definition of term: Rachis
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