Terrorism, as I've always understood it, does not have to injure people directly to be terrorism. What it has to do to qualify is affect the civilian population, whether by destroying infrastructure, killing people, whatever, as a means to convey your message to the authority.

Where a guerrilla action is against military targets with intent to render the mechanism of authority itself inoperative, a terrorist action is intended to cause the populace to be disrupted... to prey on authority's presumed need to protect its populace.