filter

1 of 2

noun

fil·​ter ˈfil-tər 

plural filters

1

a

: a porous article or mass (as of paper or sand) through which a gas or liquid is passed to separate out matter in suspension

a coffee filter

replaced the car's air filter

When air is inhaled, the oxygen is used and the remaining air is exhaled through a filter which removes the carbon dioxide.

—Hollis F. Fait et al.

b

: an apparatus containing a filter medium

If you plan to install a [water] filter, we think you should avoid one that uses powdered activated carbon in a pad.

—Consumer Reports

2

a

: a device or material for suppressing or minimizing waves or oscillations of certain frequencies (as of electricity, light, or sound)

In essence a filter is a module that takes incoming audio and removes a controllable portion of the frequency range.

—Electronic Musician

b

: a transparent material (such as colored glass) that absorbs light of certain wavelengths or colors selectively and is used for modifying light that reaches a sensitized photographic material

The photos were taken through a filter that isolates the red … light emitted by hydrogen gas.

—Astronomy

called also color filter

3

: something that selectively alters or removes like a filter (as by holding back elements or modifying the appearance of something)

Everything you eat, drink, and breathe passes through your liver. It is your body's filter.

—American Liver Foundation

(figurative) But that was only how it appeared to [Drew] Carey later on, through the filter of time and success and a lot of money.

—Richard Ouzounian

: such as

a

: a software tool that alters the appearance of a digital image

The proliferation of digitally altered images through beauty filters and face-perfecting apps has led to a reshaping and narrowing of the beauty ideal.

—Jennifer Sullivan

Since launching with still-image offerings like photo frames and filters, the app has evolved into a full creative suite …

—Alex York

Select artwork will have the option to become 'animated' when viewed through Corona's custom Instagram filter—a fun experience for guests.

—ENP Newswire

b

: software for restricting access to certain online material

The act, which … was later upheld by the U.S. Supreme Court, requires libraries and schools to install filters for obscene and pornographic material.

—Emily Gurnon

4

: the ability to refrain from expressing something (such as a thought, point of view, or belief) that may seem inappropriate, offensive, etc. to others

She was a comical woman who sometimes lacked a filter, causing the group of us to double over in laughter.

—Maddi Loiselle

"Adding the fact that he has no filter and isn't careful about what he says, which got him here in the first place, he's likely to turn off the judge and jury."

—Neama Rahmani, quoted at Newsweek.com

filter

2 of 2

verb

filtered; filtering ˈfil-t(ə-)riŋ 

transitive verb

1

: to subject to the action of a filter

2

: to remove by means of a filter

intransitive verb

1

: to pass or move through or as if through a filter

2

: to come or go in small units over a period of time

people began filtering in

Synonyms

Verb

• strain
• screen

Examples of filter in a Sentence

Noun

She smokes cigarettes with filters.

He placed a red filter on the camera lens.

digital filters that stop high-frequency sounds

Verb

They've begun filtering their water to remove impurities.

a device that filters impurities from water

sunglasses that filter ultraviolet light

Sunlight filtered through the leaves.

His ideas have filtered down to his children.

The crowd filtered into the arena.

Early election returns have begun to filter in.

Recent Examples on the Web

Noun

French astrophotographer Philippe Tosi photographed the activity on July 10 from Nîmes, France, using an H-alpha filter to capture the fine-scale action in exquisite detail. —Daisy Dobrijevic, Space.com, 11 July 2025

Fine hairs in your nose called cilia filter out dust, allergens, germs and environmental debris. —Sandee Lamotte, CNN Money, 11 July 2025

Verb

Who ventures to filter innovation from novelty? Enter the curatorial studio. —Ana María Caballero, Forbes.com, 14 July 2025

Much of it filters down from Black communities; much of it is used to trick content moderation filters; and much of it relies on an underlying comedy. —Adam Aleksic, People.com, 14 July 2025

Word History

Etymology

Noun

Middle English filtre "felt, felt carpet, piece of felt used as a filter," borrowed from Medieval Latin filtrum "felt cloth, cover or blanket of felt, piece of felt used as a filter," borrowed from *filtir (going back to *filtizō) in a West Germanic language, plural of *filt-, *felt- "felted cloth" — more at felt entry 1

Verb

derivative of filter entry 1

First Known Use

Noun

15th century, in the meaning defined at sense 1a

Verb

1576, in the meaning defined at transitive sense 1

Phrases Containing filter

• band-pass filter
• color filter
• filter bed
• filter bubble
• filter feeder
• filter paper
• filter tip
• spam filter

Rhymes for filter

• kilter
• quilter

Kids Definition

filter

1 of 2 noun

fil·​ter ˈfil-tər 

1

: a substance with pores through which a gas or liquid is passed to separate out floating matter

2

: a device containing a filter

3

: a transparent material (as colored glass) that absorbs light of some wavelengths and is used to change light (as in photography)

filter

2 of 2 verb

filtered; filtering -t(ə-)riŋ 

1

: to expose to the action of a filter

2

: to remove by means of a filter

3

: to pass through or as if through a filter

Medical Definition

filter

1 of 2 noun

fil·​ter ˈfil-tər 

1

: a porous article or mass (as of paper or sand) through which a gas or liquid is passed to separate out matter in suspension

2

: an apparatus containing a filter medium

3

a

: a device or material for suppressing or minimizing waves or oscillations of certain frequencies (as of electricity, light, or sound)

b

: a transparent material (as colored glass) that absorbs light of certain wavelengths or colors selectively and is used for modifying light that reaches a sensitized photographic material

called also color filter

filter

2 of 2 verb

filtered; filtering -t(ə-)riŋ 

transitive verb

1

: to subject to the action of a filter

2

: to remove by means of a filter

intransitive verb

: to pass or move through or as if through a filter