So much dumbfukery in here right now.
Here's the deal, it needs a couple things to be Terrorism With A Capital T. First, it needs to be politically/religiously motivated - wackos going postal don't count. Second, it needs to be part of a conspiracy - Lone Gunman type shit doesn't count. Third, it needs to be a non-State actor - if it's planned or carried out by an official national organization, it's not terrorism, it's war. Fourth, it needs to be motivated by the intent to cause terror - i.e., incentivize people to stop or start doing something. It does not get to be Terrorism just because some people got dead and others got scared, otherwise any violent crime could be classified as terrorism, and that'd get damned silly damned quick.
What happened in Colorado Springs and San Bernardino could be Terrorism. Or it might not. You need to know the motive before you can assign a label, and I don't think the actual motive in either case is publicly known yet, is it? And like I said, it matters what you call it because the administration and their Department of Thoughtcrime Homeland Security is allowed to do very unconstitutional things when it's Terrorism With A Capital T.