FILTER

filter. Filter, v.t. to strain, to pour clear off; n. a strainer

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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. 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.