A projectile is any object that's been thrown, launched, or shot through the air. Once you release a basketball toward the hoop, it becomes a projectile. When an archer shoots an arrow, when a pitcher throws a fastball, or when you toss a paper airplane across the classroom, each of these objects is a projectile.

What makes something a projectile isn't what it is, but how it's moving. The same rock sitting on the ground isn't a projectile, but the moment you throw it, it becomes one. Scientists and engineers study projectiles carefully because understanding how they move through the air helps them design everything from water fountains to spacecraft.

In physics class, you might learn that projectiles follow a curved path called a trajectory. Gravity pulls them downward while their forward motion carries them ahead, creating that familiar arc you see when you throw a ball.

As an adjective, projectile describes something that is thrown or shot, or that shoots forward suddenly, like a stream of water from a hose.