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.
any device, as a tank or tube, containing such a substance for filtering.
any of various analogous devices, as for removing dust from air or impurities from tobacco smoke, or for eliminating certain kinds of light rays.
a filter-tipped cigarette or cigar.
a lens screen of dyed gelatin or glass for controlling the rendering of color or for diminishing the intensity of light.
a circuit or device that passes certain frequencies and blocks others.
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.
to remove by the action of a filter.
to act as a filter for; to slow or partially obstruct the passage of: The thick leaves filtered the sunlight.
to pass through or as through a filter.
to pass or slip through slowly, as through an obstruction or a filter: Enemy agents managed to filter into the embattled country.