booster

booster /ˈbuːstɚ/ noun
plural boosters
booster
/ˈbuːstɚ/
noun
plural boosters
Britannica Dictionary definition of BOOSTER
[count]
1 
: something that boosts someone or something: such as
a  : an action or substance that makes something stronger or more effective
b  : something that helps or encourages someone or something
c  : booster shot
2 
US : someone who supports an idea or organization
3 
: part of a rocket that provides force for the launch and the first part of the flight