Violence at traffic stops is not terrorism, despite the fact that the majority of police fatalities occurs in them. A lunatic up on the roof shooting people at random isn't terrorism--he remains a nut. A fellow who doesn't think federal and/or state laws apply to him is delusional.
The guy who leaves an IED alongside a road and blows it with the intention of terrorizing people is a terrorist. He does't even have to holler "allahu akbar" when it blows.