In military airplane
technology, a point of the airplane where you can safely mount
something, like a bomb rack
, a missile launcher
, a gun
, or some sort of pod
The number of hardpoints and the load they are certified for is an important element of an airplane's description and it influences the missions it is capable of.
I find "hardpoint" a useful concept even in civilian life. For example, in a car the whole point of a rack is providing hardpoints.