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[fil-ter] /ˈfɪl tər/
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.
any device, as a tank or tube, containing such a substance for filtering.
any of various analogous devices, as for removing dust from air or impurities from tobacco smoke, or for eliminating certain kinds of light rays.
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.
Informal. a filter-tipped cigarette or cigar.
Photography. a lens screen of dyed gelatin or glass for controlling the rendering of color or for diminishing the intensity of light.
Electronics, Physics. a circuit or device that passes certain frequencies and blocks others.
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.
verb (used with object)
to remove by the action of a filter.
to act as a filter for; to slow or partially obstruct the passage of:
The thick leaves filtered the sunlight.
to pass through or as through a filter.
verb (used without object)
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
late Middle English
1375-1425; late Middle English filtre < Medieval Latin filtrum “felt, piece of felt used to strain liquids” < Germanic; see felt2
Related forms
filterer, noun
nonfilter, noun
overfilter, verb (used with object)
prefilter, noun
refilter, verb (used with object)
unfiltering, adjective
well-filtered, adjective
12. penetrate, sift, seep, trickle, leak. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for filterer
Historical Examples
  • If not sufficiently strong, pour out and return to the filterer.

    Housekeeping in Old Virginia Marion Cabell Tyree
  • Captain Crutchely, moreover, had a filterer for the cabin, and through it all the water used there was habitually passed.

    The Crater

    James Fenimore Cooper
  • If one quart of coffee is desired, grind three gills of coffee, put it in the filterer and pour boiling water over it.

    Housekeeping in Old Virginia Marion Cabell Tyree
British Dictionary definitions for filterer


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
any device containing such a porous substance for separating suspensions from fluids
any of various porous substances built into the mouth end of a cigarette or cigar for absorbing impurities such as tar
any electronic, optical, or acoustic device that blocks signals or radiations of certain frequencies while allowing others to pass See also band-pass filter
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
(Brit) 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
(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
(transitive) to obtain by filtering
(intransitive) foll by through. to pass (through a filter or something like a filter): dust filtered through the screen
(intransitive) to flow slowly; trickle
Word Origin
C16 filtre from Medieval Latin filtrum piece of felt used as a filter, of Germanic origin; see felt²
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
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Word Origin and History for filterer



1570s, from Medieval Latin filtrare, from filtrum (see filter (n.)). The figurative sense is from 1830. Related: Filtered; filtering.



early 15c., from Old French filtre and directly from Medieval Latin filtrum "felt," which was used to strain impurities from liquid, from West Germanic *filtiz (see felt (n.)). Of cigarettes, from 1908.

Online Etymology Dictionary, © 2010 Douglas Harper
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filterer in Medicine

filter fil·ter (fĭl'tər)

  1. A porous material through which a liquid or gas is passed in order to separate the fluid from suspended particulate matter.

  2. A device containing such a substance.

  3. Any of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or radiations of certain frequencies while passing others.

  4. A translucent screen, used in both diagnostic and therapeutic radiology, that permits the passage of rays having desirable levels of energy.

  5. A device used in spectrophotometric analysis to isolate a segment of the spectrum.

v. fil·tered, fil·ter·ing, fil·ters
  1. To pass a liquid or gas through a filter.

  2. To remove by passing through a filter.

  3. To pass through or as if through a filter.

fil'ter·er n.
fil'ter·less adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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filterer in Science
  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 © 2002. Published by Houghton Mifflin. All rights reserved.
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filterer in Culture

filter definition

A computer software program that selectively screens out incoming information.

Note: 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 Company.
Published by Houghton Mifflin Company. All rights reserved.
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