a
device, usually in connection with a
computer system whose prime function is allowing you to point to something on the screen, usually by moving some sort of visible
cursor or
pointer.
pointing devices can be used outside of window based user interfaces, for example the gpm program allows you to use the mouse to cut and paste inside the Linux console.
A pointing device can also be subverted to do something different like controlling you character in Quake ... although you may claim that in Quake one does a whole lot of pointing (and aiming and maiming).
Example of common pointing devices are: mouse, trackball, trackpad, joystick (usually associated with games), the nipple mouse/J mouse and spaceball.
There are some designs for 3D pointing devices, occasionally including force feedback, but no consensus yet.