1. Axis of a compound leaf or compound inflorescence
   "The rachis of the fern frond was dark and glossy"
    
2. The series of vertebrae forming the axis of the skeleton and protecting the spinal cord
   "the fall broke his rachis";
   - spinal column, vertebral column, spine, backbone, back

Derived forms: rachides, rachises

Type of: axis, skeletal structure

Part of: axial skeleton

Encyclopedia: Rachis