Article courtesy of Popular Science, by Kelsey D. Atherton.
Oobleck is weird, non-Newtonian goop. Made of roughly 2 parts cornstarch to 1 water (and in this case some orange coloring), the substance acts like a solid when hit and flows like a liquid when poured.
How does it react when struck by a golf ball?
Take a look:
[youtube https://www.youtube.com/embed/Sl0BHueSjvA?showinfo=0;rel=0;fs=1 expand=1]