To dream of a catapult as a weapon represents an attempt to overwhelm a problem or obstacle as quickly as possible. Doing the most impact you can as quickly as you can.
Positively, a catapult may reflect fast track ideas or choices. Overcoming obstacles with ingenuity and determination.
Negatively, a catapult may be a sign that you are taking risks or wasting time putting all you efforts into a “long shot.” Doing as much damage as you can as quickly as you can.