filter

American  

[fil-ter] / ˈfɪl tər /

noun

1. any substance, as cloth, paper, porous porcelain, or a layer of charcoal or sand, through which liquid or gas is passed to remove suspended impurities or to recover solids.

2. any device, as a tank or tube, containing such a substance for filtering.

3. any of various analogous devices, as for removing dust from air or impurities from tobacco smoke, or for eliminating certain kinds of light rays.

4. something that works like a filter, as by removing, blocking, or separating out certain elements.

   Kids often talk without a filter. Events can be distorted through the filter of memory.

5. Informal. a filter-tipped cigarette or cigar.

6. Photography.

   1. a lens screen of dyed gelatin or glass placed on a camera for controlling the rendering of color or for diminishing the intensity of light.

   2. Digital Technology. a data manipulation function that changes the color or sharpness of a digital image or overlays an additive or special effect element.

      Use a sepia filter to give your photos that old-timey look.

7. Electronics, Physics. a circuit or device that passes certain frequencies and blocks others.

8. Mathematics. a collection of subsets of a topological space, having the properties that the intersection of two subsets in the collection is a subset in the collection and that any set containing a subset in the collection is in the collection.

9. Computers. an algorithm that categorizes, sorts, prioritizes, or blocks data through rule-based protocols.

   an email filter that deletes messages with subject words found commonly in spam.

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verb (used with object)

1. to remove by the action of a filter.

2. Computers. to subject (data) to an algorithmic filter.

   The search engine will filter your query results based on your location and user profile.

3. to act as a filter for; to slow or partially obstruct the passage of.

   The thick leaves filtered the sunlight.

4. to pass through or as through a filter.

verb (used without object)

1. to pass or slip through slowly, as through an obstruction or a filter.

   Enemy agents managed to filter into the embattled country.

   Synonyms:

   leak, trickle, seep, sift, penetrate

filter British  

/ ˈfɪltə /

noun

1. a porous substance, such as paper or sand, that allows fluid to pass but retains suspended solid particles: used to clean fluids or collect solid particles

2. any device containing such a porous substance for separating suspensions from fluids

3. any of various porous substances built into the mouth end of a cigarette or cigar for absorbing impurities such as tar

4. any electronic, optical, or acoustic device that blocks signals or radiations of certain frequencies while allowing others to pass See also band-pass filter

5. any transparent disc of gelatine or glass used to eliminate or reduce the intensity of given frequencies from the light leaving a lamp, entering a camera, etc

6. a traffic signal at a road junction consisting of a green arrow which when illuminated permits vehicles to turn either left or right when the main signals are red

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verb

1. (often foll by out) to remove or separate (suspended particles, wavelengths of radiation, etc) from (a liquid, gas, radiation, etc) by the action of a filter

2. (tr) to obtain by filtering

3. to pass (through a filter or something like a filter)

   dust filtered through the screen

4. (intr) to flow slowly; trickle

filter Scientific  

/ fĭl′tər /

1. A material that has very tiny holes and is used to separate out solid particles contained in a liquid or gas that is passed through it.

2. A device that allows signals with certain properties, such as signals lying in a certain frequency range, to pass while blocking the passage of others. For example, filters on photographic lenses allow only certain frequencies of light to enter the camera, while polarizing filters allow only light polarized along a given plane to pass. Radio tuners are filters that allow frequencies of only a narrow range to pass into an amplification circuit.

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filter Cultural  

1. A computer software program that selectively screens out incoming information.

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Discover More

Spam may be the target of a filter, or parents may use a filter designed to prevent their child's access to pornographic or violent Web pages.

Other Word Forms

• filterer noun
• nonfilter noun
• overfilter verb (used with object)
• prefilter noun
• refilter verb (used with object)
• unfiltering adjective
• well-filtered adjective

Etymology

Origin of filter

First recorded in 1375–1425; late Middle English filtre, from Medieval Latin filtrum “felt, piece of felt used to strain liquids,” from Germanic; felt ²

Explanation

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.

Example Sentences

So getting with friends of mine, who are comedians and I always filter it through them, like, what’s funny, what’s not.

From Los Angeles Times • Apr. 14, 2026

These network costs will filter through to household energy bills.

From BBC • Apr. 10, 2026

It also acquired parachute maker Pioneer Aerospace in 2023 and specialty RF filter firm Akoustis in 2025 after each of those companies filed for bankruptcy.

From MarketWatch • Apr. 2, 2026

No one can predict how long the Iran war will last, how it might affect global energy prices, and how it might filter through to the American economy.

From The Wall Street Journal • Mar. 26, 2026

The modern population of the world now hears all music through the filter - some would say imperfection - of Equal Temperament.

From "The Story of Music" by Howard Goodall

Related Words

• clean
• drain
• dribble
• leak
• penetrate
• percolate
• permeate
• refine
• sift
• trickle
• winnow