booster

(bo͞oˈstər)

1. One that boosts, as:
   a. A device for increasing power or effectiveness.
   b. An enthusiastic promoter, as of a sports team or school.
   c. Electronics A radio-frequency amplifier.
   d. The primary stage of a multistage rocket that provides the main thrust for launch, liftoff, and initial flight.
2. A booster shot.
3. Slang One who steals goods on display in a store.