n.
Pronunciation: ' bü-st ə r
Function: noun
Date: 1888
: one that boosts: as a : an enthusiastic supporter b : an auxiliary device for increasing force, power, pressure, or effectiveness c slang : SHOPLIFTER d : a radio-frequency amplifier for a radio or television receiving set e : the first stage of a multistage rocket providing thrust for the launching and the initial part of the flight f : a substance that increases the effectiveness of a medicament especially : BOOSTER SHOT