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

Etymology

Origin of booster

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

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

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

Ely is looking at installing small booster cells on lamp-posts, which would cost less than a mast and not interfere with the city's landscape.

From BBC ● Sep. 29, 2026

The huge first-stage booster, called "Super Heavy," will fall shortly after launch into waters of the Gulf of Mexico.

From Barron's ● Sep. 28, 2026

At the same time, schools wouldn’t be allowed to use booster clubs to funnel money to athletes under the guise of paying them for “name, image and likeness” rights.

From The Wall Street Journal ● Sep. 25, 2026

The fans clutched in their hands the 1988 Permian football yearbook, published annually by the booster club to help generate funds for the program.

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

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

Thefts in L.A. were already surging when Milwaukee-based boosters launched their “Kia Boys” videos in the summer of 2021, and had begun to level off by time the meme hit national news a year later.

From Los Angeles Times ● Sep. 15, 2026

Even if you have a model as old as the iPhone 11, there’s plenty of practical improvements for you in iOS 27, not to mention performance boosters, such as up to 80% faster AirDrop transfers.

From The Wall Street Journal ● Sep. 14, 2026

A.I. company CEOs, employee whistleblowers and industry boosters can’t stop crowing about the dangers posed by the products they’re rushing to create.

From Salon ● Sep. 12, 2026

Then I hit the throttle and the twin rocket boosters in each of the robot’s feet ignited, launching it upward, out of my stronghold and into Falco’s star-filled sky.

From "Ready Player One: A Novel" by Ernest Cline

Related Words

• backer
• enthusiast
• patron
• promoter