Auto hunting is defined as the advancement or potential advancement of your character without your active and conscious control of that character's actions. For example, putting a rock on your space bar so that your character can kill monsters without your attention is auto hunting.
The use of custom macros is also considered auto hunting. This includes the use of macros for the advancement of any skill.
The penalty for using macros is severe. Possible banishment waits for those found to be using such macros.