Just uncritically accepting the government's definition of a powerful term like 'terrorism' is a massive mistake. They're intentionally defined in a way that means the state can't be pegged with them - here because it specifies 'unlawful', yet the state dictates what is lawful.

What this means is that, say, simply fighting back against the cops during a protest can be framed as 'terrorism' since it's 'violence against persons to intimidate or coerce for political objectives', but the cops attacking you isn't since it's 'legal'.

A US soldier invading Iraq can't be a 'terrorist' since the US itself of course thinks that the invasion was 100% totally legal, but the people fighting back against him? They sure can be!
Always interrogate the way powerful entities monopolise emotionally charged words.