Here's how Bill Walsh defined it. (It's a rollout, sprint-out or "waggle.")
Action Pass
The third category of pass that most people use is what we call the action pass, where your quarterback moves outside. There are a couple of reasons for moving outside. One certainly is to avoid the inside pass rush. For a dropback passing team we'll sprint-out "waggle" as we call it-outside to avoid blitzers who approach straight up the field on us. The other advantage is to bring yourself closer to the potential receiver.
We'll get outside to throw the ball and get ourselves closer to the man we want to throw to. When you can get outside, the trajectory of the ball can be flatter because normally there isn't a man between you and the receiver.
The versatility also includes changing your formations. We continuously change receiver width and spacing. We seldom will line up our receiver with the same spacing on two or three plays in a row. If we want to throw the ball to the outside, we will reduce the split of the receiver. We need running room to the outside. We don't want the ball in the air very long. If we want to throw inside, we will extend the split of our receivers, so that there is more maneuvering room to the inside, and spread the defense. Our backs, as many teams know will cheat to get where they have to be. We know that if we throw to backs, the first thing on their mind is how to release out of the backfield. We are quite willing to move the man to get the release and sometimes telegraph what we are doing. We are quite willing to do that with the idea that when we want to break a given tendency, we simply line them up there and run something else."