Bruce Schneier has a great essay about the fact that NSA spying apologists say that dragnet surveillance is limited to cases of terrorism: but "terrorism" is now synonymous with "whatever it is people we want to spy on are doing."
Back in 2002, the Patriot Act greatly broadened the definition of terrorism to include all sorts of "normal" violent acts as well as non-violent protests. The term "terrorist" is surprisingly broad; since the terrorist attacks of 9/11, it has been applied to people you wouldn't normally consider terrorists.
The most egregious example of this are the three anti-nuclear pacifists, including an 82-year-old nun, who cut through a chain-link fence at the Oak Ridge nuclear-weapons-production facility in 2012. While they were originally arrested on a misdemeanor trespassing charge, the government kept increasing their charges as the facility's security lapses became more embarrassing. Now the protestors have been convicted of violent crimes of terrorism -- and remain in jail.
Meanwhile, a Tennessee government official claimed that complaining about water quality could be considered an act of terrorism. To the government's credit, he was subsequently demoted for those remarks.
Mission Creep: When Everything Is Terrorism (Thanks, Bruce!)