The Collaborative International Dictionary of English v.0.48:

Filter \Fil"ter\, v. t. [imp. & p. p. Filtered; p. pr. & vb.
   n. Filtering] [Cf. F. filter. See Filter, n., and cf.
   Filtrate.]
   To purify or defecate, as water or other liquid, by causing
   it to pass through a filter.
   [1913 Webster]

   Filtering paper, or Filter paper, a porous unsized paper,
      for filtering.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Filter \Fil"ter\, v. i.
   To pass through a filter; to percolate.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Filter \Fil"ter\, n.
   Same as Philter.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Filter \Fil"ter\, n. [F. filtre, the same word as feutre felt,
   LL. filtrum, feltrum, felt, fulled wool, this being used for
   straining liquors. See Feuter.]
   Any porous substance, as cloth, paper, sand, or charcoal,
   through which water or other liquid may passed to cleanse it
   from the solid or impure matter held in suspension; a chamber
   or device containing such substance; a strainer; also, a
   similar device for purifying air.
   [1913 Webster]

   Filter bed, a pond, the bottom of which is a filter
      composed of sand gravel.

   Filter gallery, an underground gallery or tunnel, alongside
      of a stream, to collect the water that filters through the
      intervening sand and gravel; -- called also infiltration
      gallery.
      [1913 Webster]

WordNet (r) 3.0 (2006):

filter
    n 1: device that removes something from whatever passes through
         it
    2: an electrical device that alters the frequency spectrum of
       signals passing through it
    v 1: remove by passing through a filter; "filter out the
         impurities" [syn: filter, filtrate, strain, separate
         out, filter out]
    2: pass through; "Water permeates sand easily" [syn:
       percolate, sink in, permeate, filter]
    3: run or flow slowly, as in drops or in an unsteady stream;
       "water trickled onto the lawn from the broken hose"; "reports
       began to dribble in" [syn: trickle, dribble, filter]

The Free On-line Dictionary of Computing (19 January 2023):

filter

   1. (Originally Unix, now also MS-DOS) A program that
   processes an input data stream into an output data stream in
   some well-defined way, and does no I/O to anywhere else except
   possibly on error conditions; one designed to be used as a
   stage in a pipeline (see plumbing).  Compare sponge.

   2. (functional programming) A higher-order function which
   takes a predicate and a list and returns those elements of
   the list for which the predicate is true.  In Haskell:

    filter p []     = []
    filter p (x:xs) = if p x then x : rest else rest
    	   where
    	   rest = filter p xs

   See also filter promotion.

   [Jargon File]


The Jargon File (version 4.4.7, 29 Dec 2003):

filter
 n.

    [very common; orig. Unix] A program that processes an input data stream
    into an output data stream in some well-defined way, and does no I/O to
    anywhere else except possibly on error conditions; one designed to be used
    as a stage in a pipeline (see plumbing). Compare sponge.