An action in which one is almost always ready to do a group activity, but when it comes time to show up, they always have a reason not to participate. Most people know or have known a backpedaler at one point or another.
Lily: Oh man, lets all participate in a fun party game or event!
Everyone else: Wow! That sounds like a great idea, lets do it!
Lily: Haha... Actually i don't want to do that, but i'll watch!
Everyone else: You need a new set of tires after backpedaling that hard