YO: When referring to “Orthodox”, it is simply referencing the Jews who never broke off to form a new movement. In other words, “Orthodox” is simply referring to what used to simply be called “Judaism”. (This point is also true regarding the term “Chareidi”.)
In fact, the very term “Orthodox” was coined and invented by the Maskilim (intended in a mocking manner, based on Orthodox Christianity) to refer to those who didn’t join the breakaway Reform movement.