booster
noun [ C ] uk/ˈbuː.stər/ us/ˈbuː.stɚ/
(IMPROVEMENT)
促进提高的事物；起推动作用的事物
something that improves or increases something
a confidence/morale booster 对信心／士气的激励
(ENGINE)
（航天器的）推进器
an engine on a spacecraft that gives extra power for the first part of a flight
a rocket booster 火箭推进器
(DRUG)
（增强药效的）辅助药剂
a small amount of a substance that is given to increase the effect of the same substance given some time before, to continue to protect a person from illness
a polio booster 小儿麻痹症辅助药剂