Prefilter

noun
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.
3.
any of various analogous devices, as for removing dust from air or impurities from tobacco smoke, or for eliminating certain kinds of light rays.
4.
Informal. a filter-tipped cigarette or cigar.
5.
Photography. a lens screen of dyed gelatin or glass for controlling the rendering of color or for diminishing the intensity of light.
6.
Electronics, Physics. a circuit or device that passes certain frequencies and blocks others.
7.
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)
8.
to remove by the action of a filter.
9.
to act as a filter for; to slow or partially obstruct the passage of:
The thick leaves filtered the sunlight.
10.
to pass through or as through a filter.
verb (used without object)
11.
to pass or slip through slowly, as through an obstruction or a filter:
Enemy agents managed to filter into the embattled country.
noun
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
3.
any of various porous substances built into the mouth end of a cigarette or cigar for absorbing impurities such as tar
4.
any electronic, optical, or acoustic device that blocks signals or radiations of certain frequencies while allowing others to pass See also band-pass filter
5.
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
6.
(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
verb
7.
(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
8.
(transitive) to obtain by filtering
9.
(intransitive) foll by through. to pass (through a filter or something like a filter): dust filtered through the screen
10.
(intransitive) to flow slowly; trickle

filter fil·ter (fĭl’tər)
n.

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.

v. fil·tered, fil·ter·ing, fil·ters

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.

fil’ter·er n.
fil’ter·less adj.
filter
(fĭl’tər)

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.

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.