: one that boosts: such 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 or dose used to renew or increase the effect of a drug or immunizing agent
especially
: booster shot
Examples of booster in a Sentence
These exercises are real metabolism boosters.
Music is my favorite mood booster.
A sincere compliment can be a true confidence booster.
The university has a number of wealthy boosters who contribute generously each year.
a new design for rocket boosters
Recent Examples on the Web
For now, Starship has made eight suborbital launch attempts and managed three successful captures of the Super Heavy booster.
—
Richard Tribou, The Orlando Sentinel, 23 May 2025
Although Covid-19 boosters are no longer licensed for healthy people aged 64 and under, the new policy leaves the door open for those who still want to get additional doses of the vaccine.
—Elizabeth Yuko, Rolling Stone, 21 May 2025
The editorial also pointed out that COVID booster uptake over the past two seasons has been low, with fewer than one-quarter of Americans receiving shots each year — ranging from less than 10 percent of children younger than 12 in the 2024–2025 season, to 50 percent of adults over 75.
—Tom Gavin, EverydayHealth.com, 21 May 2025
With their party facing record low approval ratings, many top Democrats are trying to reposition themselves from Biden boosters to truth-tellers of what really happened in 2024.
—Michael Barbaro, New York Times, 20 May 2025
See All Example Sentences for booster
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Richard Tribou, The Orlando Sentinel, 23 May 2025
Although Covid-19 boosters are no longer licensed for healthy people aged 64 and under, the new policy leaves the door open for those who still want to get additional doses of the vaccine.
—Elizabeth Yuko, Rolling Stone, 21 May 2025
The editorial also pointed out that COVID booster uptake over the past two seasons has been low, with fewer than one-quarter of Americans receiving shots each year — ranging from less than 10 percent of children younger than 12 in the 2024–2025 season, to 50 percent of adults over 75.
—Tom Gavin, EverydayHealth.com, 21 May 2025
With their party facing record low approval ratings, many top Democrats are trying to reposition themselves from Biden boosters to truth-tellers of what really happened in 2024.
—Michael Barbaro, New York Times, 20 May 2025
See All Example Sentences for booster
Cite this Entry
“Booster.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/booster. Accessed 3 Jun. 2025.
Copy CitationKids Definition
booster
noun
boost·er
ˈbü-stər 
1
: one that boosts
2
: an enthusiastic supporter
3
4
: a device for strengthening radio or television signals
5
: the first stage of a multistage rocket providing force for the launching and the first part of the flight
Medical Definition
booster
noun
boost·er
ˈbü-stər
: a substance or dose used to renew or increase the effect of a drug or immunizing agent: such as
a(1)
(2)
b
: synergist sense 1
a chemical acting as a booster to sulfa drugs
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