I loathe the term "app" for anything outside of a mobile device. To me an app is a chopped down minimal piece of software meant to run on a device of limited capability such as a phone or tablet. It makes me cringe the way Microsoft is calling all software "apps" now, it feels like that awkward old guy trying to fit in with a group of teenagers by (mis)using their slang.
As an old-school Mac user, I hate the connotation of the modern definition of "app". On the Mac, we always used the word "application" for an executable (with some minor exceptions, like desk accessories and control panels), and it was common for us to abbreviate "application" to "app". And that's where the iOS app store got its name, ultimately!
Unfortunately, the rest of the IT world hadn't really ever encountered the word "app" before and mistakenly understood it to mean a slimmed-down mobile app. But with the explosion of smartphones, well, we're stuck with that now.