booster

(noun) a person who backs a politician or a team etc.. Synonyms: supporter, protagonist, champion, admirer, friend. Examples: "All their supporters came out for the game." "They are friends of the library."

(noun) someone who is an active supporter and advocate. Synonyms: promoter, plugger.

(noun) a thief who steals goods that are in a store. Synonyms: shoplifter, lifter.

(noun) an amplifier for restoring the strength of a transmitted signal. Synonyms: booster amplifier, booster station, relay link, relay station, relay transmitter.

(noun) the first stage of a multistage rocket. Synonyms: booster rocket, booster unit, takeoff booster, takeoff rocket.

(noun) an additional dose that makes sure the first dose was effective. Synonyms: booster dose, booster shot, recall dose.