As others already pointed out, there isn't really a unified agreed upon definition of terrorism, but the vast majority those definitions overlap, with small differences between them here and there.

The probably most important part of those definitions is that the implementation of terror against your opponents has political motivations. War crimes in general on the other hand mostly don't follow this same philosophy. The only modern day example that theoretically checks both boxes at once is stuff like the Russian terror bombing of civilians (the war crime part), thinking they'll eventually bomb them into total submission and Russia will achieve their political goals (the terrorism part).