> terrorist is an armed combatant who explicitly strikes at civilians instead of at their government

Uhm, no. This is closer to the definition of terrorism, but it's still not it. Drug store robbery gone violent involves armed people who may explicitly strike a civilian shop owner who turned out to have a gun under the counter.

Terrorism is about intent: to spread terror. If you're blowing a bomb up just to see the bodies fly, you're not a terrorist. But if you're conjuring an alien monster abomination to prevent a nuclear war between two super-powers through _terror_ against an imaginary alien adversary, you are a terrorist (although in this case one could argue that you indeed do it for the greater good).