Its not a rocket because its not propelled by its own motor.
I think its more like a mortar bomb.
Just my view, somebody out there knows.
Quatermass
Additional. A projectile is any object propelled through space by the exertion of a force, which ceases after launch. In a general sense, even a football or baseball may be considered a projectile. It can cause damage (injury, property damage) to a person, animal or object it hits, depending on factors including size, shape, speed and hardness. Accordingly, in practice most projectiles are designed as weapons.
The above shows that 'projectile' is a bit vague in terms of a desription. Shot or shell is better.