Entry 2 senses Webster, 1913 Rachis /(rā"kĭs)/ · Ra·chis · IPA /ˈɹeɪkɪs/ 01 n. The spine; the vertebral column. pl. Rachises, Rachides ((rā"kĭs*ĕz)) 1. The spine; the vertebral column.(Anat.) 2. Same as Rhachis.(Bot. & Zool.) See: Rhachis