You
should know then!
Here's GNU's definition of a Unix-like, "A Unix-like operating system is a software collection of applications, libraries, and developer tools, plus a program to allocate resources and talk to the hardware, known as a kernel." This is a very heavy idea of an OS and grep and emacs sound like "developer tools" and "applications". Most OS people involved in unix-like OSs would be aghast if you didn't at least include some basic userspace applications like cat and ls.
GNU isn't specific about what needs to be in the collection of things to constitute a unix-like OS, but it looks like that agrees in most respects to bookwormAT, "'operating system' is a very generic expression. For most people today an operating system is the software that is installed on the device minus applications that the user installed himself."
GNU's concept is miles different from very light concepts of an embedded OS's like Femto OS which near as I can tell is pretty much just a kernel and some libraries.
WP on the other hand says, "An operating system (OS) is a collection of software that manages computer hardware resources and provides common services for computer programs." So strictly speaking, by this definition an OS doesn't even need to provide disk access like the old DOSs!
Although of course it later contradicts itself and says "Access to data stored on disks is a central feature of all operating systems." which anybody involved in the OS community knows is not a central feature of "all" operating systems. I've used OSs where useful file system access was provided via userspace applications (a la FUSE).
Palantir takes the position that an OS doesn't need to be interacting or managing the hardware stuff, just providing the ability to run different hosted applications is enough, making things like web browsers operating systems (http://www.palantir.com/2009/11/palantir-like-an-operating-s...)
bookwormATs position is that not only are OSs heavy things, but that "Android" is not just an OS, but a meta-OS description of what an Android OS should be (just like XML is a meta-language for describing XML compatible file formats).
So if GNU's definition is correct (and lots of people subscribe to GNU's position), bookwormATs position, "'operating system' is a very generic expression. For most people today an operating system is the software that is installed on the device minus applications that the user installed himself." is correct.