> Palestine Action has been designated a terrorist group in the UK as well after sabotaging military aircraft (the article says they sprayed paint, but does not say it was sprayed inside jet engines, rendering them inoperable).

That pretty much tells you everything you need to know. Definitions of "terrorism" that extend to sabotage against occupying or invading militaries and their allies are meaningless and hollow dilutions. At that point the discourse has been reduced to something like "violence is scary".

This use is also interesting (and galling) because it frames disarming as an unacceptably violent act.

There are some definitions of terrorism that leave room to designate attacks against professional agents of state violence as "terror", e.g., attacks on soldiers who are off-duty, attacks on civilian police forces, attacks on nominally civilian intelligence organizations like the CIA, etc.

Imo such uses of the words "terror" and "terrorism" should be considered carefully, because sometimes they are meaningful or useful, but often they are essentially attempts to hoodwink the public. Effectively they are designed so that any attack against an occupying army by a faction too weak to muster a permanent standing army of equal strength falls into the "terrorism" category, which means invasion is "war" but resistance is "terrorism".

The notion of "civilian" or "non-combatant" isn't always straightforward, either. In the history of the PKK, for example, one of the "civilian" forces targeted by bombings and shootings were a local militia whose sole purpose was suppressing popular unrest among local Kurdish populations who were forbidden from speaking their own native languages, celebrating their holidays, etc. Formally these militias were not part of an army. But their scarcely concealed function was suppression of the local population, unlike (for example) a proper civilian police force whose role is at least nominally to promote public safety, assist vulnerable (weak, elderly, disabled) citizens with daily life, investigate crimes, mediate/de-escalate disputes, etc.

Anyway, it's worth sitting down and thinking through a few different serious definitions of terrorism and asking yourself what use they are. One or more definitions will likely stand out to you as particularly useful when it comes to thinking through things like the safety of innocents, the morality and bounds of acceptable political activism, and other topics that might directly affect your comfort and safety. You'll often find that governments and large press organizations try to trade on the emotional impact of those definitions while operating under rather different ones that are more convenient for themselves.