I have heard this term frequently used, but I haven't been able to find a definition, even in the extensive Wikipedia Article on Schnitzel.
The article you linked to references this dish as "Wiener Schnitzel". That article defines it as veal--pounded, breaded, and fried--garnished with lemon, and served with potatoes.
"Wiener" refers to its Viennese origin, and Schnitzel to the type of preparation (pounded, breaded, and fried). There are many varieties of Schnitzels, made of several different meats, and with various sauces. Jaeger Schnitzel, for examples, is served with a creamy mushroom sauce. The one from Vienna is served with lemon and potatoes.