We're in agreement. The term "terrorism" should only be applied to violent acts that have the express purpose of spreading terror for political and/or military ends.

It is ironic that while the 9/11 attacks gave a clear illustration of the meaning of the term "terrorism", the reaction of Bush & co. had the effect of blurring and weakening the meaning of the term, as it came to be applied in a hyperbolic way to any action a user of the term didn't like. (Mis)Users of the term usually being power-holders, or their supporters.

Clearly these pirates aren't terrorists (did someone suggest they were?) - they are not even particularly violent, from what I can see.

As for the American Revolutionaries - someone who knows their history better may correct me on this, but it is my impression that there were both Loyalist and Revolutionary guerilla bands operating off the beaten track who engaged in what we would today call, legitimately, terrorism.