Definitions for "Approach angle"
In side-view, the angle between the ground and a line, ahead of the vehicle, joining the periphery of the front wheel and (typically) the front bumper or other low component. It represents the size or steepness of a slope or obstacle that can be approached or climbed without striking bodywork.
The angle at which you set the boat when about to enter the current. For example when ferry gliding and breaking in and out of the current.
as a vehicle approaches a grade, it's the angle of slope which it can climb up without any part of the front (bumper, shackle etc.) hitting the ground/rock