Definition - to become very angry
The Latin word ballista, which referred to a missile-throwing siege engine of yore, is the root of our ballistic. The earliest meaning of the word in English, “of or relating to the science of the motion of projectiles in flight,” is closely tied to its Latin origin. Ballistic was taken on additional meanings over the years, including “being or characterized by repeated bouncing” (referring to exercise), “capable of resisting or stopping bullets or other projectiles” (referring to a material), and “extremely and usually suddenly excited, upset, or angry” (usually referring to people).
Go ballistic is a fairly recent idiom, dating from the 1980s, and may also be used to mean “to become very excited.”
He-Man has a magic sword. When he holds it to the sky, gets struck by lightning a few times and thunders, “ have the power!,” it really brings the house down. The kids go ballistic, and the phrase echoes down the halls of even the most staid elementary schools.
— Washington Times (Washington, DC), 24 Oct. 1984