A thrower is someone who throws something. Athletes who compete in track and field events like the shot put, discus, or javelin are called throwers. These athletes train to hurl heavy objects as far as possible, using their whole body to generate power and speed.

In baseball, a pitcher might be called a thrower, especially if they focus more on throwing hard than on pitching strategically. A scout might say “he's just a thrower, not really a pitcher yet” to mean the player can throw the ball fast but hasn't mastered the art of outsmarting batters.

The word can describe anyone who throws anything: a quarterback throwing a football, a potter working at a pottery wheel (since potters who shape clay are sometimes called throwers), or even someone tossing a frisbee at the park. Context tells you what kind of throwing is happening. When your friend claims to be a “good thrower” at recess, they probably mean they can throw a ball accurately and with good distance, not that they're training for the Olympics.