- 1an imaginary line through the center of an object, around which the object turns Mars takes longer to revolve on its axis than the earth does.
- 2 (technology) a fixed line against which the positions of points are measured, especially points on a graph the vertical/horizontal axis The real cost is measured along the horizontal axis and the quantity of labor is measured along the vertical axis. The main road is on a north-south axis.
- 3(geometry) a line that divides a shape into two equal parts an axis of symmetry The axis of a circle is its diameter.
- 4 [usually singular] (formal) an agreement or alliance between two or more countries the Axis Powers of World War II