[ax.is] n, pl ax.es [L, axis, axle; akin to OE eax axis, axle, Gk axon, Lith asis, Skt aksa] (14c) 1 a: a straight line about which a body or a geometric figure rotates or may be supposed to rotate b: a straight line with respect to which a body or figure is symmetrical--called also axis of symmetry c: a straight line that bisects at right angles a system of parallel chords of a curve and divides the curve into two symmetrical parts d: one of the reference lines of a coordinate system
2. a: the second vertebra of the neck on which the head and first vertebra turn as on a pivot b: any of various central, fundamental, or axial parts
3: a plant stem
4: one of several imaginary lines assumed in describing the positions of the planes by which a crystal is bounded and the positions of atoms in the structure of the crystal
5: a main line of direction, motion, growth, or extension
6. a: an implied line in painting or sculpture through a composition to which elements in the composition are referred b: a line actually drawn and used as the basis of measurements in an architectural or other working drawing 7: any of three fixed lines of reference in an aircraft that run in the longitudinal, lateral, and vertical directions, are mutually perpendicular, and usu. pass through the aircraft's center of gravity 8: partnership, alliance Axis adj (1938): of or relating to the three powers Germany, Italy, and Japan engaged against the Allied nations in World War II