what does the word ballistic mean in the phrase intercontinental ballistic missile?
It used to mean unguided. So the missile would be aimed like a mortar, fueled up like a powder charge (or a timed ignition programmed), and then let loose. Math determined it's accuracy. But it doesn't seem that the term ballistic has ever been dropped, has it. Everything seems to be a "ballistic" missile. Maybe someone military can chime in, you have an interesting question.
The missile is launched upwards, but the end of its flight is powered by gravity (free fall).