The trouble with providing a "clear definition" is that this concept is still a bit fuzzy for myself, and I fear by trying to nail it too closely down I might lose out of something I think really would be worthwhile to include, or include things that really pollutes the conversation around the concept (like GMPC or Buddy). If I would have to make an attempt of it now it would be something like "Benevolient GM stance the phenomenom of having a temporary situation where the GM is actively trying to help out the player characters in a way that is in no way disruptive of the desired play experience of the group as a whole". I think this formulation at least includes firefighting in groups where this is accepted/expected, and excludes GMPCs and unwanted Buddying. So as such this definition seem promising?