WordReference Random House Learner's Dictionary of American English © 2026
fil•ter /ˈfɪltɚ/USA pronunciation
n. [countable]
v.
fil•ter•er, n. [countable]
WordReference Random House Unabridged Dictionary of American English © 2026- Chemistryany substance, such as cloth, paper, or charcoal, through which liquid or gas is passed to remove impurities or to trap solids:The spring water goes through a filter before it is bottled.
- Chemistryany device containing a substance for filtering.
- Photographya lens screen of colored glass used in photography to control the color or to diminish the intensity of light.
v.
- to remove by the action of a filter:[~ + object]The dehumidifier filters moisture out of the air.
- to act as a filter for; to slow the passage of:[~ + object]The dehumidifier filters the air.
- to pass or slip through slowly:[no object]Sunlight was filtering through the trees.
- [no obj] to reach gradually:Day by day, news filtered out about the catastrophe.
fil•ter•er, n. [countable]
fil•ter
(fil′tər),USA pronunciation n.
v.t.
v.i.
fil′ter•er, n.
- Chemistryany 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.
- Chemistryany 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 Termsa filter-tipped cigarette or cigar.
- Photographya lens screen of dyed gelatin or glass for controlling the rendering of color or for diminishing the intensity of light.
- Electronics, Physicsa circuit or device that passes certain frequencies and blocks others.
- Mathematicsa 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.
- 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.
v.i.
- to pass or slip through slowly, as through an obstruction or a filter:Enemy agents managed to filter into the embattled country.
- Gmc; see felt2
- Medieval Latin filtrum felt, piece of felt used to strain liquids
- late Middle English filtre 1375–1425
- 11. penetrate, sift, seep, trickle, leak.