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.

Informal . a filter-tipped cigarette or cigar.

Photography . a lens screen of dyed gelatin or glass for controlling the rendering of color or for diminishing the intensity of light.

Electronics, Physics . a circuit or device that passes certain frequencies and blocks others.

Mathematics . 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.

verb

collect , combine

verb

clarify , clean , distill , drain , dribble , escape , exude , filtrate , leak , metastasize , ooze , osmose , penetrate , percolate , permeate , purify , refine , screen , sieve , sift , soak through , strain , trickle , winnow , infiltrate , leach , seep , strainer , transude