Booster (electric power), a motor-generator set used for voltage regulation in direct current electrical power circuits
Booster (rocketry), used in space flight to provide or augment the main thrust in the initial phase of the rocket's flight
Booster, a co-channel repeater in broadcasting, used to improve signal strength
Booster, technically an alternative term for an electronic power amplifier, but with slightly different meaning depending on the technical field in which it is used
Booster dose, or booster shot, in medicine, a vaccination given after a previous vaccination
Booster engine, extra cylinders on a steam locomotive, driving the trailing truck or a tender truck, to give more power on starting