1 an imaginary line through the centre of an object, around which the object turns:
Mars takes longer to revolve on its axis than the earth.
2 (technical) a fixed line against which the positions of points are measured, especially points on a GRAPH:
the vertical / horizontal axis * The real wage is measured along the horizontal axis and the quantity of labour 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 [usuallysing.] (formal) an agreement or ALLIANCE between two or more countries:
the Franco-German axis
