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

The same solid rocket booster (SRB) technology and components used during the space shuttle era have been refitted to power SLS. —Josh Dinner, Space.com, 30 Jan. 2026

When unsure, the safest course is to consult your doctor about a booster, which is safe for most adults. —Jesse Pines, Forbes.com, 30 Jan. 2026

The booster flew for the 17th time (3rd booster to do so) and landed on the droneship Just Read the Instructions. —Richard Tribou, The Orlando Sentinel, 30 Jan. 2026

Kilmeade, a Trump booster who knows the president often watches the morning show, volunteered the idea again at 7:15 and once more at 8:10. —Brian Stelter, CNN Money, 26 Jan. 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