English Reference
noun · verb

booster

n. · v.
US /ˈbustɝ/ UK /bˈuːstɐ/ boost·er UK spelling boosters

  1. 01 B2 Upper Intermediate Medicine

    n.an extra dose of a vaccine given to keep the protection working.

    n.an additional dose of a vaccine or immunising agent administered to maintain or increase the level of immunity.

    Simple

    The doctor recommended a booster before I travelled to a country with high infection rates.

    In context

    Public health officials debated the optimal timing for the booster to ensure maximum antibody response across the elderly population.

    Usage

    Often used as a compound noun: 'booster shot'.

    booster shotre vaccination
  2. 02 B2 Upper Intermediate Science

    n.the first part of a rocket that provides the power to lift off.

    n.the initial stage of a multistage rocket or an auxiliary engine providing supplemental thrust during liftoff.

    Simple

    The rocket's boosters fell away into the ocean once the craft reached the upper atmosphere.

    In context

    Engineers monitored the solid rocket boosters closely during the first two minutes of flight to ensure the trajectory remained within safety parameters.

    thrusterrocket motor
  3. 03 C1 Advanced American English

    n.someone who actively supports or promotes a team, school, or person.

    n.an enthusiastic supporter or promoter of a specific cause, institution, or individual.

    Simple

    The local business boosters raised money to renovate the high school football field.

    In context

    As a lifelong booster of the university's arts programme, she donated a significant portion of her estate to the new gallery.

    Teacher's tip

    In the US, this often refers specifically to members of a 'booster club' who raise money for school sports.

    criticdetractor
  4. 04 B2 Upper Intermediate

    n.a small seat placed on a chair or car seat to help a child sit higher.

    n.a removable seat used to raise a child to a height where they can sit at a table or safely use a car seatbelt.

    Simple

    The restaurant provided a booster so the toddler could reach the table.

    In context

    Safety regulations require children of a certain height to remain in a booster until the vehicle's shoulder belt fits them correctly.

    booster seat
  5. 05 C2 Proficiency AcademicTechnical Linguistics

    n.a word like 'very' or 'extremely' that makes another word stronger.

    n.a lexical item used to amplify or strengthen the force of an utterance.

    Simple

    In the sentence 'I am so happy', the word 'so' acts as a booster.

    In context

    The researcher analysed the frequency of boosters in persuasive writing to determine how they influenced the reader's perception of authority.

    intensifieramplifier
    downtonerhedge
  6. 06 C2 Proficiency SlangAmerican English

    n.a person who steals items from a shop.

    n.a person who engages in shoplifting or professional theft.

    Simple

    The security guard caught the booster trying to leave with three expensive jackets.

    In context

    The police identified a ring of professional boosters who had been targeting high-end boutiques across the metropolitan area.

    shoplifterthief
  7. 07 C1 Advanced Informal Medicine

    v.to give someone an extra medical dose to keep them protected.

    v.to administer a booster dose of a vaccine to an individual.

    Simple

    The clinic is planning to booster all the residents at the nursing home next week.

    In context

    The health department aimed to booster the entire vulnerable population before the winter flu season peaked.

    re vaccinate

My excitement was impossible to contain and as the rocket fired its huge boosters and engines and headed skywards, my reaction went viral.

BBC News· 11 Apr 2026

Earlier this month, SpaceX launched one of its reusable Falcon 9 boosters for a record-setting 35th time.

Ars Technica· 9 Jul 2026
This entry
Level B2 · Upper Intermediate
Frequency Frequent
Updated