booster

American  

[boo-ster] / ˈbu stər /

noun

• boosters
  plural

1. a person or thing that boosts, especially an energetic and enthusiastic supporter.

2. Electricity. 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 especially a helper locomotive.

4. Military. an explosive more powerful than a primer, for ensuring the detonation of the main charge of a shell.

5. Rocketry.

   1. a rocket engine used as the principal source of thrust in the takeoff of a rocket or missile.

   2. 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. Also called booster shot, booster dose. Medicine/Medical. a dose of an immunizing substance given to maintain or renew the effect of a previous one.

7. Pharmacology. 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.

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booster British  

/ ˈbuːstə /

noun

1. a person or thing that supports, assists, or increases power or effectiveness

2. Also called: launch vehicle. the first stage of a multistage rocket

3. radio television

   1. a radio-frequency amplifier connected between an aerial and a receiver to amplify weak incoming signals

   2. a radio-frequency amplifier that amplifies incoming signals, retransmitting them at higher power

4. another name for supercharger

5. short for booster dose

6. slang a shoplifter

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booster Scientific  

/ bo̅o̅′stər /

1. An additional dose of an immunizing agent, such as a vaccine or toxoid, given at a time period of weeks to years after the initial dose to sustain the immune response elicited by the first dose. Tetanus, diphtheria, and measles vaccines are commonly given in booster doses.

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Usage

What is a booster shot? A booster shot is an additional dose of a vaccine given to a person in order to maintain or renew the effect of a previous dose. This is sometimes called a booster dose (especially since vaccines aren’t always given via shots) or simply a booster. Vaccines strengthen the body’s immunity against disease. They work by introducing a killed, weakened, or otherwise modified version of a specific disease (such as a virus or bacterium) so that the body’s immune system will produce antibodies that will destroy those specific pathogens if they ever enter the body again. A booster shot basically refreshes the immune system’s memory of a disease in order to strengthen immunity—it “boosts” the existing defenses. Booster shots are commonly given to both children and adults. Common vaccines that typically involve one or multiple booster shots include those against tetanus, hepatitis A, human papillomavirus (HPV), and measles, mumps, and rubella (MMR). The timing of the booster shot varies depending on the vaccine—some are given a few months after the initial dose, while others are given years later. Medical organizations such as the Centers for Disease Control and Prevention (CDC) provide immunization schedules that recommend the frequency of booster shots.

Other Word Forms

Derived Forms

• boosterish
  adjective

Inflected Forms

Nouns

• boosters
  plural

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Etymology

Origin of booster

An Americanism dating back to 1885–90; boost + -er ¹

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Explanation

If you’re a big fan and promoter of something or someone, you're a booster. Go team! A booster provides support, like a kid’s booster seat, a follow-up dose of medicine, or a booster rocket that launches the Space Shuttle. Boosters of teams, groups, or organizations often form official clubs to coordinate their fundraising and event planning. Another kind of booster is an engine or rocket that's the first stage of launching a space vehicle into orbit. And in medicine, a booster is a second (or subsequent) dose of a vaccine that helps the initial dose work better. All of these boosters assist, encourage, or boost in some way.

Example Sentences

See Examples For:

booster boosters

While exports were the key "booster", the third quarter was "particularly difficult" for China, as retail performance was weak and fixed-asset investment declined, Dan Wang, a director on Eurasia Group's China team, told AFP.

From Barron's ● Oct. 15, 2026

I urge all who are eligible to come forward for their flu jab, their COVID-19 booster and their RSV vaccine.

From BBC ● Oct. 13, 2026

Silva was hired by the team booster club to take the photos, which were intended to be enjoyed by the players and their family.

From Los Angeles Times ● Sep. 30, 2026

The mission was expected to help SpaceX test a slew of improvements to Starship and its Super Heavy booster, setting up what the company called the “next phase” of making the rocket fully reusable.

From MarketWatch ● Sep. 28, 2026

The serpent’s body was as thick as a booster rocket, glinting with coppery scales.

From "The Titan's Curse" by Rick Riordan

United Airlines Chief Executive Scott Kirby, now one of Starlink’s biggest boosters, also faced Musk’s ire before becoming a customer.

From The Wall Street Journal ● Oct. 2, 2026

The bill was supported by the California News Publishers Assn., of which the Los Angeles Times is a member and a wide range of other community news boosters.

From Los Angeles Times ● Sep. 30, 2026

Unlike other Michigan boosters, the Ellisons weren’t interested in sideline passes or VIP seats because they don’t attend games.

From The Wall Street Journal ● Sep. 18, 2026

So far, A.I. boosters have been quick to take credit when their models hit a new benchmark in email-writing or 3D modeling.

From Salon ● Sep. 12, 2026

To the boosters, that story was music to their ears, further confirmation that when the middle of December rolled around they would be on their way to Texas Stadium for the state championship.

From "Friday Night Lights: A Town, A Team, And A Dream" by H.G. Bissinger

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Related Words

• backer
• enthusiast
• patron
• promoter

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