Comment by stetrain

As far as I know in this case both sides have already attacked each other via bombs, airstrikes, rockets, etc. I'm not really making a judgement on whether this was ethical or justified.

There's just a distinction to be made from intentionally killing civilians for the purpose of causing terror versus targeting a group that you are in an open military hostility with. The second one, as you say, is basically just war. And war has historically also included civilian casualties.

Flying a plane full of civilians into a building full of civilians, or detonating a bomb in a public square full of civilians, are pretty clear examples of what "terrorism" is. They aren't actions meant to directly attack the capability of an enemy to wage war against you.

What governments and media choose to label "terrorism" or "terrorist groups" however is inherently political and not done following some agreed, objective definition.