mouse-wheel-mode

mouse-wheel-mode is a variable defined in `mwheel.el'.
Its value is

t

Documentation:
Non-nil if Mouse-Wheel mode is enabled.
See the command `mouse-wheel-mode' for a description of this minor mode.
Setting this variable directly does not take effect;
either customize it (see the info node `Easy Customization')
or call the function `mouse-wheel-mode'.

You can customize this variable.