What does booster mean?
A booster is something that strengthens, amplifies, or renews whatever it is applied to. In everyday modern usage it most often refers to an additional dose of a vaccine given months or years after the original immunization, designed to restore fading protection against disease. The word also describes devices that increase physical power or intensity — a rocket booster provides extra thrust at launch, a signal booster improves mobile reception, and a voltage booster raises electrical output. Beyond these technical senses, a booster can be a person: an enthusiastic supporter who promotes a sports team, a hometown, or a charitable cause with energy and loyalty. Derived from the verb "boost," meaning to lift or increase, the noun carries a broadly positive connotation of improvement and encouragement. Whether describing a medical injection, an engineering component, or a devoted fan, a booster is fundamentally about giving extra force to something already in motion.
nounA thing or person that boosts something — that increases its strength, effectiveness, or progress. Most commonly, an additional dose of a vaccine given to renew or strengthen immunity, or a device that amplifies a signal, pressure, or thrust.
- An additional dose of a vaccine given after the initial series to maintain or renew immunity.
- A person who actively supports, promotes, or champions something such as a team, town, or cause.
- A device that increases the power, force, or intensity of something, such as a rocket booster, a signal booster, or a voltage booster.
- An extra dose of medicine or drug beyond the usual amount to intensify its effect.
- (Informal, chiefly US) A shoplifter, especially one who steals habitually from stores.
"Health officials urged everyone over sixty to get a flu booster before winter."
"She rolled up her sleeve for her COVID-19 booster at the pharmacy on Saturday morning."
"The rocket's first-stage boosters detached and fell back toward Earth two minutes after launch."
Standard regular plural; used across all senses of the noun.
"The launch vehicle was fitted with four solid-fuel boosters."
The word 'booster' was popularized in 19th-century America by railroad towns whose 'booster' citizens aggressively promoted local growth — giving us the term 'boosterism'.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of booster
Booster derives from the American English verb "boost," which emerged in the early nineteenth century meaning to lift or push someone upward, likely by analogy with "boom." The noun "booster" developed in late nineteenth-century America to mean a person who energetically promotes their town or business, a usage that gave rise to the phenomenon known as "boosterism." From this sense of adding extra push came the later applications to rockets, signals, and, in the twentieth century, supplementary vaccine doses.
Related word forms
How booster is actually used
In medical contexts, "booster" almost always means a follow-up vaccine dose and is frequently shortened in speech to just "booster" rather than "booster shot" or "booster dose." In informal American English, especially in retail-loss-prevention jargon, it can refer to a habitual shoplifter, though this sense is less familiar to most readers.
Easily confused with booster
A rooster is a male chicken; a booster is something that increases strength, immunity, or support.