The Pink (aka Justin) calls this Articulation. " look mom the articulation is awesome"

I call it weird-whatever-okay then...

An articulated vehicle is a vehicle which has a permanent or semi-permanent pivoting joint in its construction, allowing the vehicle to turn more sharply. There are many kinds of articulated vehicles, from heavy equipment to buses, trams and trains. Steam locomotives were sometimes articulated in that the driving wheels could pivot around turns.

In a broader sense, any vehicle towing a trailer could be described as articulated (the word articulated comes from the Latin articulus : small joint). In the UK, the term "articulated lorry" refers to the combination of a tractor and a semi-trailer, abbreviated to "artic". In the U.S., this is called a semi-trailer truck, "tractor-trailer" or "semi-truck" and would not necessarily be called articulated.