The phrase "rotation axis" refers to an imaginary line around which an object turns or spins. It is like an axle or a pole running through the object's center, allowing it to rotate or revolve. Full definition
We measure an inclination between the projected planetary orbital axis and the projected stellar rotation axis of lambda = -26.9 + / - 4.6 deg, indicating a moderate inclination of the planetary orbit. (arxiv.org)
This succession of glacials and interglacials is caused by changes in insolation brought about by cyclical variations in the distance between Earth and the Sun and in the tilt and direction of our planet's rotation axis relative to the Sun. (sciencedaily.com)
«This asymmetry depends on properties such as the mass and the relative orientation of the back holes» rotation axes before the merger,» said team member Colin Norman of STScI and Johns Hopkins University. (sciencedaily.com)