I came across this great example of an action indicator the other day. It is one of my cats (and not the Beast of Exmoor). An action indicator is pretty much what it sounds like - it is an indicator of an action. In this case the print on the right shows a turning motion indicating a change in direction.
I think it is clear that the print on the right looks as if it has been twisted in the mud - which is of course exactly what it has done! Any questions just post a comment!