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 [as modifier]: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.
booster in other Oxford dictionaries
Definition of booster in the US English dictionary
