A booster is something that increases power, strength, or effectiveness. In rocketry, boosters are powerful engines that provide extra thrust during liftoff, helping rockets escape Earth's gravity. Space shuttles used massive solid rocket boosters strapped to their sides, which fell away once the shuttle reached a higher altitude.

In medicine, a booster is an additional dose of a vaccine given after the original shots to strengthen your immunity. Just like reviewing math facts helps you remember them better, a booster shot reminds your immune system how to fight off specific diseases.

A booster can also be a person who actively supports something. School boosters organize fundraisers, attend games, and promote school programs. They boost morale and resources. A booster club might sell spirit wear or run concession stands to raise money for the team.

The word captures the idea of giving something an extra push or lift. A booster seat raises small children higher in cars so seatbelts fit properly. A confidence booster is anything that makes you feel more self-assured. When something needs more energy, support, or strength to succeed, that's when you need a booster.