Other forms: filtered; filtering; filters

A machine or device that removes dangerous or unwanted materials from a substance passing through it is called a filter. A kitchen water filter makes the water safer to drink — and also taste better.

Cars have many different filters, each of which takes impurities out of air, fuel, or water before it enters the car's engine. Most coffee makers require paper filters that allow brewed coffee to flow into the pot while leaving the coffee grounds behind. Filter is also a verb, meaning to strain or remove particular particles. The Medieval Latin root is filtrum, or "felt," which was used by early chemists to strain liquids, especially when purifying water.

Definitions of filter
  1. noun
    device that removes something from whatever passes through it
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    air cleaner, air filter
    a filter that removes dust from the air that passes through it
    bacteria bed
    layer of sand or gravel used to expose sewage effluent to air and the action of microorganisms
    coffee filter
    filter (usually of paper) that passes the coffee and retains the coffee grounds
    drain basket
    a filter in a sink drain; traps debris but passes water
    filter bed
    filter consisting of a layer of sand or gravel for filtering water
    fuel filter
    a filter in the fuel line that screens out dirt and rust particles from the fuel
    diffusing screen, light filter
    a transparent filter that reduces the light (or some wavelengths of the light) passing through it
    oil filter
    a filter that removes impurities from the oil used to lubricate an internal-combustion engine
    a filter to retain larger pieces while smaller pieces and liquids pass through
    water filter
    a filter to remove impurities from the water supply
    glass wool
    glass fibers spun and massed into bundles resembling wool
    diatomaceous earth, diatomite, kieselguhr
    a light soil consisting of siliceous diatom remains and often used as a filtering material
    colander, cullender
    bowl-shaped strainer; used to wash or drain foods
    filter tip
    an air filter on the end of a cigarette; contains material that filters the smoke
    screen, sieve
    a strainer for separating lumps from powdered material or grading particles
    a device to keep back tea leaves when pouring a cup of tea
    type of:
    an instrumentality invented for a particular purpose
  2. verb
    remove by passing through a filter
    filter out the impurities”
    synonyms: filter out, filtrate, separate out, strain
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    type of:
    divide into components or constituents
  3. verb
    pass through
    synonyms: percolate, permeate, sink in
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    pass into or through by filtering or permeating
    cause (a liquid) to enter by penetrating the interstices
    type of:
    penetrate, perforate
    pass into or through, often by overcoming resistance
  4. verb
    run or flow slowly, as in drops or in an unsteady stream
    synonyms: dribble, trickle
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    leach, percolate
    permeate or penetrate gradually
    type of:
    course, feed, flow, run
    move along, of liquids
  5. noun
    an electrical device that alters the frequency spectrum of signals passing through it
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    high-pass filter
    a filter that passes frequencies above a certain value and attenuates frequencies below that value
    low-pass filter
    a filter that passes frequencies below a certain value and attenuates frequencies above that value
    type of:
    electrical device
    a device that produces or is powered by electricity




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