The word cast has several related meanings:

1. To throw something, often with force or purpose. A fisherman casts a line into the water, sending the hook flying out with a smooth motion of the rod. You might cast stones into a pond to watch them skip, or cast a net to catch fish. The word suggests a deliberate, sweeping motion rather than just tossing something carelessly.
2. To assign roles in a play, movie, or show. When a director casts a production, she chooses which actors will play which characters. The group of actors chosen is called the cast. Getting cast in the school musical means you've been selected for a part.
3. To shape something by pouring hot liquid metal or other material into a mold. Sculptors cast bronze statues by pouring melted bronze into specially shaped containers and letting it harden. Factories cast engine parts the same way. A cast-iron skillet is made by pouring molten iron into a mold.
4. A hard shell placed around a broken bone to keep it still while healing. If you break your arm, doctors might put a cast on it: a hard, protective covering made from plaster or fiberglass that holds the bone in place for weeks while it mends.