filter

A device which separates a suspended, dissolved, or particulate matter from a fluid, solution, or other substance; any device that separates one substance from another.

Noun

A device which separates a suspended, dissolved, or particulate matter from a fluid, solution, or other substance; any device that separates one substance from another.
- Then add four drops of crocodile semen, and pass the mixture through a filter. - 1961, Harry E. Wedeck, Dictionary of Aphrodisiacs, New York: The Citadel Press, page 152:
Electronics or software that separates unwanted signals (for example noise) from wanted signals or that attenuates selected frequencies.
Any item, mechanism, device, or procedure that acts to separate or isolate.
- He runs an email filter to catch the junk mail.
- In America alone, people spent $170 billion on “direct marketing”—junk mail of both the physical and electronic varieties—last year. Yet of those who received unsolicited adverts through the post, only 3% bought...
Self-restraint in speech.
- He's got no filter, and he's always offending people as a result.
- These were women with enormous feelings and, almost always, no filter to mediate their expression of them. - 2026 January 30, Judy Berman, “Catherine O’Hara Portrayed the Vain and Delusional With a Radical Lack of...
A non-empty upper set (of a partially ordered set) which is closed under binary infima (a.k.a. meets).
- The collection of cofinite subsets of ℝ is a filter under inclusion: it includes the intersection of every pair of its members, and includes every superset of every cofinite set.
- If (1) the universal set (here, the set of natural numbers) were called a "large" set, (2) the superset of any "large" set were also a "large" set, and (3) the intersection of a pair of "large" sets were also a "large"...
A translucent object placed in the light path of a camera to remove certain wavelengths (colors), or a computer program that simulates such an effect.
An appearance-altering digital image effect.
- He don't need no filter posting pictures! - 2013, Patent Pending, “All-Star Hipster”, in Brighter:

Origin

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.

Verb

To sort, sift, or isolate.
- This strainer should filter out the large particles.
- “You have probably never seen anything like this before, Mr. Toler. It is baleen, or if you prefer it, whalebone, taken from the mouth of the bowhead whale. It is used by the whale to filter its food.” - 1954, Alexander...
- Receivers often incorporate digital equalisers to 'mop up' slight intersymbol interference after initial filtering at the receiver. - 1992, Chris C. Bissell, David A. Chapman, Digital signal transmission (2nd edition),...
To diffuse; to cause to be less concentrated or focused.
- The leaves of the trees filtered the light.
To pass through a filter or to act as though passing through a filter.
- The water filtered through the rock and soil.
To move slowly or gradually; to come or go a few at a time.
- The crowd filtered into the theater.
To ride a motorcycle between lanes on a road
- I can skip past all the traffic on my bike by filtering.
To be discouraged where a connoisseur or hardcore fan would not.
- Most people get filtered by that episode.