Filter

n.	1.	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. 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.
v. t.	1.	To purify or defecate, as water or other liquid, by causing it to pass through a filter. [imp. & p. p. Filtered ; p. pr. & vb. n. Filtering] Filtering paper a porous unsized paper, for filtering.
v. i.	1.	To pass through a filter; to percolate.
n.	1.	Same as Philter.

Noun	1.	filter - device that removes something from whatever passes through it
	2.	filter - an electrical device that alters the frequency spectrum of signals passing through it
Verb	1.	filter - remove by passing through a filter; "filter out the impurities" Synonyms: filter out, filtrate, separate out, strain
	2.	filter - pass through; "Water permeates sand easily" Synonyms: permeate, sink in, percolate
	3.	filter - 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" Synonyms: dribble, trickle

1.		filter - (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.		filter - (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.

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