tumbleweed
The remains of any of a number of species of plants that die and break off from their roots as part of their life cycle. In this state, tumbleweeds are blown across the landscape by the wind, spreading their seeds as they tumble.
A tumbleweed's presence means either that the area is vacant or that there's nothing going on, such that the rolling tumbleweed is the most exciting or interesting event at that point.
