I don't understand what the big deal is about side spin though?
Obviously by definition, spin axis is tilted = side spin. The End.
Deformation is correct terminology especially from former tennis coaches of mine. They alwass said deformation of the ball at the tennis racquet.
I wonder what actually causes the spin axis to become tilted that way, or rather, why does side spin afffect the ball-flight the way it does?
I guess it's because the way that the dimple pattern on the golfball, affects the lift force of golf ball? If the spin is tilted, then lift is mis-directed I suppose...?
If you roll an aircraft along its roll axis with the flightstick say... 30 deg to the left. Roll axis is controlled by flight surfaces called ailerons, which are at the backsides of each wing.
The airflow becomes disturbed and the aircraft starts to turn towards the left side, quite slowly usually though...
I suppose, the reason that the aircraft turns because of roll axis flight surfaces, is that the lift is disturbed
You can see the aileron position when looking at an aircraft from the outside e.g. watch US Navy Hornet F-18 before take-off. Usually the pilot "tests" the flight surfaces by jerking the controls, while still on the ground. (so the ground crew can check if the flight surfaces work properly according to control inputs))