[ fil-ter ]
See synonyms for: filterfilteredfiltering on

  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.

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

  2. 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.

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

  4. Photography.

    • 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.

    • 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.

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

  6. 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.

  7. 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.

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.

  1. to act as a filter for; to slow or partially obstruct the passage of: The thick leaves filtered the sunlight.

  2. 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.

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; see origin at felt2

Other words for filter

Other words from filter

  • fil·ter·er, noun
  • non·fil·ter, noun
  • o·ver·fil·ter, verb (used with object)
  • pre·fil·ter, noun
  • re·fil·ter, verb (used with object)
  • un·fil·ter·ing, adjective
  • well-filtered, adjective

Words Nearby filter Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use filter in a sentence

British Dictionary definitions for filter


/ (ˈfɪltə) /

  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

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

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

  3. 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

  4. British 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

  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

  1. (intr foll by through) to pass (through a filter or something like a filter): dust filtered through the screen

  2. (intr) to flow slowly; trickle

Origin of filter

C16 filtre from Medieval Latin filtrum piece of felt used as a filter, of Germanic origin; see felt ²

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for filter


[ fĭltər ]

  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.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for filter


A computer software program that selectively screens out incoming information.

Notes for filter

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.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.