The IMF is the second largest military on the planet. next only to the US, (who often use the IMF to do their dirty work).
Terrorism is using fear for political ends.
Plane hi-jacking has traditionally been terrorism. Give us money, or we kill all these people. Release these prisoners, or we will kill all these people. Whatever the demands.
Did the attackers on September 11th issue demands? Were they trying to instill fear, or were they fighting what they saw as a holy war?
Terrorism is an attempt at coercion, not just an attack.
There are many warmongers in the US, and most are willfully blind to it. If taken as an act of war, the attacks on September 11th, 2001 were the second on US soil in over 100 years, yet the US has taken up arms on other nations soil with ONGOING campaigns over 50 times in the past 65 years. Somehow, it gets seen as a "Terrorist" attack, like someone is trying to bully them.