verb (used with object)

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.

Nearby words

  1. filoselle,
  2. filosus,
  3. filovirus,
  4. fils,
  5. filt.,
  6. filter bed,
  7. filter bubble,
  8. filter cake,
  9. filter factor,
  10. filter feeder

Origin of filter

1375–1425; late Middle English filtre < Medieval Latin filtrum “felt, piece of felt used to strain liquids” < Germanic; see felt2

Related forms Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for filter

British Dictionary definitions for filter



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 passSee 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
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


(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
(tr) to obtain by filtering
(intr foll by through) to pass (through a filter or something like a filter)dust filtered through the screen
(intr) to flow slowly; trickle

Word Origin for 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

Word Origin and History for filter
Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for filter




A porous material through which a liquid or gas is passed in order to separate the fluid from suspended particulate matter.
A device containing such a substance.
Any of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or radiations of certain frequencies while passing others.
A translucent screen, used in both diagnostic and therapeutic radiology, that permits the passage of rays having desirable levels of energy.
A device used in spectrophotometric analysis to isolate a segment of the spectrum.


To pass a liquid or gas through a filter.
To remove by passing through a filter.
To pass through or as if through a filter.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for filter



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.
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.

Culture definitions for filter


A computer software program that selectively screens out incoming information.


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.