You're wrong, all those WWII resistance fighters were by definition terrorists to germans/japanese. Its just that US marketing over-used the term in past decade and a half to label anybody inconvenient as a justified target for extermination because 'national security'

Except that to some extent, they do. When my country was occupied by the Nazi Germany, people who fought back were called freedom fighters by us. They were called terrorists by the Nazis.

Sure, but I don't think that extent is useful for the purposes of this discussion.

FWIW, you and I are likely from the same country.

My point being, one country's terrorist is another country's freedom fighter. There is some nuance here, but we're talking about somewhat random and indiscriminate murder of civilians who may or may not be connected to a military group in hopes people at large will stop supporting that group. There's a political agenda in there, and there's death of innocent civilians. There's strong element of fear too - I remember reading articles about drone strikes in Pakistan years ago, in which it was reported that the locals developed a fear of clear blue sky. A fear of good weather, because that's when drones come.

If one objects to calling it terrorism because they're really trying to hit the combatants only, and objects to calling it a war crime because technically there's no war with an internationally recognized nation state, then how should we call it?