Something that boosts.

Short for booster seat.

The first stage of a multistage rocket that provides the thrust for liftoff and the initial flight.

A motor-generator set used for voltage regulation in direct current electrical power circuits.

Someone who is a fan or supporter of something.

Someone who promotes a town or business.

A member of a booster club.

(immunology) A booster dose.

(explosives) A small quantity of a sensitive explosive that is triggered by a detonator and provides the energy needed to detonate a larger quantity of a less-sensitive explosive.

(linguistics) A term that serves to amplify or strengthen an utterance, such as "really".

(video games) A power-up item.

(gaming) A package of cards or figurines designed to add to a player's collection.

(slang) A thief.

(rail transport) A booster engine fitted to a steam locomotive.

(transitive, medicine) To give a booster shot to; to boost.