Okay, so what IS a terrorist then?

Last night I saw an item on cable news relating the story of a gunman/grenadist in Belgium that killed five and wounded 125 people. The reporter was quick to interject that the guy was "not a terrorist".

That got me thinking.

Just because a fellow hasn't pledged allegiance to Hamas, Al Quaeda or SEIU; it doesn't mean he's not a terrorist. Clearly anyone who practices mayhem on large groups of people is a terrorist; regardless of his motives or affiliations.  Do we need the government to classify terrorists for us now?