Pronunciation: (bOO'stur),[key] —n. 1. a person or thing that boosts, esp. an energetic and enthusiastic supporter.
2. Elect.a device connected in series with a current for increasing or decreasing the nominal circuit voltage.
3. Railroads.any machine, device, phenomenon, etc., that helps to move a train, as a tailwind, downgrade, roller bearings, or esp. a helper locomotive.
4. Mil.an explosive more powerful than a primer, for ensuring the detonation of the main charge of a shell.
5. Rocketry. a. a rocket engine used as the principal source of thrust in the takeoff of a rocket or missile.
b. the first stage containing this engine and its fuel supply, which may or may not be detached from the rocket when the fuel has been consumed.
6. Med.Also called boost'er dose", boost'er shot". a dose of an immunizing substance given to maintain or renew the effect of a previous one.
7. Pharm.a chemical compound, medicinal substance, or the like, that serves as a synergist.
8. a radio-frequency amplifier for connecting between a radio or television antenna and the receiving set to intensify the received signal.
9. an auxiliary pump, used in a pipeline or other system, to add to or maintain a prevailing amount of pressure or vacuum.
10. Slang.a shoplifter or petty thief.