A person who controls the direction of a vehicle, such as a ship or a car.
A steerer is someone who helps to keep things going in the right direction.
Examples:
The steerer of the ship made sure it went the right way.
The car's steerer turned left.
The steerer is important for keeping the ship safe.
The steerer of the car made a funny face.
The steerer of the spaceship made sure it didn't crash into the moon.
The steerer of the bike was very good at it.