Appatic

The answer is:

Pretty much everything on/off/from the web is now a app in one way or another.

Be it a service, an add-on to a service or a service solution to another service. There are many examples and the most common one could be search.

Search is an App because it process the query for what you are looking for and delivers you a response in a specific pre-defined way from which you go elsewhere. It is utilitarian.

If it delivered what you were looking for depends on both if you used it well and if the search engine actually knows what to display based on what you searched for.

But that is beyond the point.

The only thing left to do is to categorize and tag what kind of App is and how it is distributed and how/where it is meant to be used.

App as a Solution/Service or Service/Solution as a App. Kind of a chicken vs egg dilemma when it comes to start ups today.

Well, You get the idea from my petty rationalization.

Most of the times over simplifying or over generalizing is bad. In this case is just to make a point.