You are correct what is a widow maker.I've always understood widow makers to be pieces of tree tops or limbs either snagged or dubiously attached in a tree that is not immediately obvious to those underneath, and of particular hazard to tree fallers, etc. Sure, a leaning tree could be considered a widow maker I suppose, but in those cases, the hazard and or risk of being around or under it is relatively obvious and can be avoided as necessary.
But in some cases, being able to walk or drive around a widow maker may not be so easy. Where I live, there are fences, that impede walking around such obstacles. So I am saying, it is complicated. And if the land owner, or the "government" does not deal with it... I have been know to do so. Even at legal risk to myself.
Hope this helps.