Synonyms for booster

a person who backs a politician or a team etc. (noun)

• supporter
• protagonist
• champion
• admirer
• friend

someone who is an active supporter and advocate (noun)

• promoter
• plugger

a thief who steals goods that are in a store (noun)

• shoplifter
• lifter

an amplifier for restoring the strength of a transmitted signal (noun)

the first stage of a multistage rocket (noun)

an additional dose that makes sure the first dose was effective (noun)