1. A protuberance (process or projection) of the axis (second cervical vertebra). It exhibits a slight constriction or neck, where it joins the main body of the vertebra. The condition, where the dens is separated from the body of the axis, is called os odontoideum, and may cause nerve and circulation compression syndrome. (wikipedia.org)
2. A toothlike process at the back of 2nd vertebra of the neck. (wordnetweb.princeton.edu)
3. A small, toothlike, upward projection from the second vertebra of the neck around which the first vertebra rotates. (The American Heritage® Dictionary of the English Language)
4. The toothlike process on the upper surface of the axis, which articulates with the atlas above. (biology-online.org)
Syn: Dens, odontoid peg