axis /ak″sēz/ pl. axes [Gk, axon, axle] , 1. (in anatomy) a line that passes through the center of the body, or a part of the body, such as the frontal axis, binauricular axis, and basifacial axis. 2. the second cervical vertebra, about which the atlas rotates, allowing the head to be turned, extended, and flexed. Also called epistropheus, odontoid vertebra.
