axis

ax·is

noun \ˈak-səs\

plural ax·es \-ˌsēz\

Definition of AXIS

1

a : a straight line about which a body or a geometric figure rotates or may be thought of as rotating b : a straight line with respect to which a body, organ, or figure is symmetrical

2

a : the second vertebra of the neck of the higher vertebrates that is prolonged anteriorly within the foramen of the first vertebra and united with the dens which serves as a pivot for the atlas and head to turn upon—called also epistropheus b : any of various central, fundamental, or axial parts <the cerebrospinal axis> <the skeletal axis> c : axilla