Pronunciation: (fil'tur),[key] —n. 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. Photog.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. Math.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.
—v.t. 1. to remove by the action of a filter.
2. to act as a filter for; to slow or partially obstruct the passage of: The thick leaves filtered the sunlight. 3. to pass through or as through a filter.
—v.i. to pass or slip through slowly, as through an obstruction or a filter: Enemy agents managed to filter into the embattled country.