A catapult is something that hurls things through the air, like a catapult that sends pumpkins flying in an annual Halloween competition.
To pronounce catapult, accent the first syllable: "CAT a pult." Catapult can also be a verb that means "to hurl or shoot forward." It's not only objects that catapult. A hit single can catapult a band to great fame, for example, or a high score may catapult you into first place. Just don't catapult any cats. That would catapult you to notoriety, and probably also to jail.