Source : Webster's Revised Unabridged Dictionary (1913)

Rachis \Ra"chis\, n.; pl. E. {Rachises}, L. {Rachides}. [NL.,
   fr. Gr. ? ?.] [Written also {rhachis}.]
   1. (Anat.) The spine; the vertebral column.

   2. (Bot. & Zo["o]l.) Same as {Rhachis}.

Source : WordNet®

rachides
     See {rhachis}