English Reference
noun · verb

filter

n. · v.
US /ˈfɪɫtɝ/ UK /fˈɪltɐ/ fil·ter UK spelling filter's, filter's, philtre

  1. 01 B1 Intermediate

    n.a device that removes dirt or unwanted pieces from a liquid or gas.

    n.a porous device or substance used to separate suspended particulate matter from a fluid.

    Simple

    You need to change the water filter every six months to keep the water clean.

    In context

    The industrial ventilation system utilizes a high-efficiency particulate air filter to ensure the laboratory remains free of contaminants.

    Usage

    often used with 'water', 'air', or 'coffee' as a modifier.

    strainersievepurifier
  2. 02 A2 Elementary Computing

    n.a software tool that changes how a photo or video looks, often used on social media.

    n.a digital image processing effect that alters the appearance of a photograph or video stream.

    Simple

    She used a vintage filter to make her new photos look like they were from the 1970s.

    In context

    Social media platforms offer a variety of augmented reality filters that can modify facial features in real-time during video calls.

  3. 03 B2 Upper Intermediate Informal

    n.the ability to think before you speak so you do not say something rude or inappropriate.

    n.the psychological or social capacity for self-censorship and restraint in verbal communication.

    Simple

    Sometimes he says exactly what he thinks because he has no filter.

    In context

    In casual settings, her lack of a social filter is charming, but it can be problematic during formal business negotiations.

    Usage

    usually used with 'no' or 'a' in phrases like 'he has no filter'.

  4. 04 B1 Intermediate

    v.to pass a liquid or gas through a device to clean it.

    v.to pass a substance through a medium to remove impurities or specific components.

    Simple

    The sunlight was filtered by the thick leaves of the trees.

    In context

    The kidneys work constantly to filter waste products from the blood and maintain chemical balance.

  5. 05 B2 Upper Intermediate

    v.to move or spread slowly, often a few people or things at a time.

    v.to move, seep, or communicate gradually or in small quantities.

    Simple

    News about the company's closing began to filter out to the employees.

    In context

    After the concert ended, the audience began to filter out of the stadium and into the nearby subway stations.

    Usage

    often used with prepositions like 'through', 'in', or 'out'.

  6. 06 C1 Advanced British English

    v.to ride a motorcycle or bicycle between lanes of slow-moving cars.

    v.to navigate a two-wheeled vehicle between lanes of stationary or slow-moving traffic.

    Simple

    The motorcyclist filtered through the heavy traffic to reach the front of the queue.

    In context

    While filtering is legal in many jurisdictions, riders must exercise extreme caution when passing between large commercial vehicles.

    lane splitting

The government is advising people , external to either use indirect viewing methods or wear genuine eclipse glasses with specially designed filters that meet international safety standards ISO 12312-2:2015(E).

BBC News· 12 Aug 2026

The models it tested were granted access to the internet, and the AISI also disabled in-built filters that would usually block dangerous cyber-attacks.

BBC News· 6 Aug 2026

From Middle English filtre, from Medieval Latin filtrum (compare also Old French feutre (“felt; filter”)), from Frankish filtir, from Proto-West Germanic felt. See felt. Doublet of phin.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin gmw-pro *felt
Level C1 · Advanced
Frequency Common
Updated