My definition of RTW, admittedly biased towards the places I have lived, would require passing through a point in Europe and a point in Aus/NZ/Polynesia/Melanesia.

I'd also probably settle for any route with a stopover/transit point north of the Tropic of Cancer and another south of the Tropic of Capricorn. Route must also pass through Greenwich meridian and International Date Line.

RTW tickets have many different conditions, but I'm sure there are many here who can describe them in far more detail than I could do.