Comment by bodhiandphysics

The security council defines terrorism as "…criminal acts, including against civilians, committed with the intent to cause death or serious bodily injury, or taking of hostages, with the purpose to provoke a state of terror in the general public or in a group of persons or particular persons, intimidate a population or compel a government or an international organization to do or to abstain from doing any act, which constitute offences within the scope of and as defined in the international conventions and protocols relating to terrorism…"

the crucial lines is "provoe a state of terror in the general public." That is to say, terrorism uses arbitrary violence in order to cause fear and panic leading to political goals. By contrast, the targets of this attack were directly against the personnel and leadership of a militarized organization currently in a shooting war with israel. The goal is not to instill terror in a population, but to directly target the capabilities of a military organization.

Note that doesn't mean its not a war crime (I don't think it is but...)! It could still be a war crime for all sorts of reasons... it just means it's not terrorism.