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 ]

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 ]

v. i. To pass through a filter; to percolate. [ 1913 Webster ]

n. Same as Philter. [ 1913 Webster ]

adj. having a tip designed to filter the smoke; -- of a cigarette or cigar; as, filter-tipped cigarettes. [ WordNet 1.5 +PJC ]