booster

noun

boost·​er ˈbü-stər 

: 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

Synonyms of booster

• proponent
• supporter
• advocate
• advocator
• exponent
• promoter

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

It was later recycled by Obama, who in 2010 directed NASA to pursue the SLS as a new moon-capable rocket, including the use of engines and solid rocket boosters used from the Space Shuttle Program. —Richard Tribou, The Orlando Sentinel, 6 Feb. 2026

But despite his success in locating the Apollo 16 rocket booster impact site in 2015, evidence of Luna 9 remained elusive. —Ilya Ferapontov, Scientific American, 5 Feb. 2026

Agrawal said Roos boosters are already planning to invest more into the program. —Pj Green, Kansas City Star, 5 Feb. 2026

Most adults who were vaccinated as children don’t need a booster, experts say, but adults who didn’t get the shots as kids can still get vaccinated. —Mary Ramsey, Charlotte Observer, 5 Feb. 2026

Word History

First Known Use

1888, in the meaning defined above

Phrases Containing booster

• booster cushion
• booster dose
• booster seat
• booster shot

Rhymes for booster

• rooster

Kids Definition

booster

noun

boost·​er ˈbü-stər 

1

: one that boosts

2

: an enthusiastic supporter

3

: booster shot

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)

: booster shot

(2)

: booster dose

b

: synergist sense 1

a chemical acting as a booster to sulfa drugs