Learn how to say Boosters correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word booster:
1a device for increasing electrical voltage or signal strength.
2the first stage of a rocket or spacecraft, used to give initial acceleration and then jettisoned.
3 Medicine a dose of a vaccine that increases or renews the effect of an earlier one:
boosters at five-year intervals are recommended
a booster injection
4 [in combination] a source of help or encouragement:
job fairs are a great morale booster
North American a keen promoter of a person, organization, or cause.
5North American informal a shoplifter.