—filter /ˈfɪl.tər/ aep /-t̬ɚ/
noun [C] (EQUIPMENT)
► C2 any of several types of equipment or devices for removing solids from liquids or gases, or for removing particular types of light: » a water filter» a dust filter» I like to experiment with different light filters on my camera.» Ozone is the Earth's primary filter for ultraviolet radiation.See picture: oil filter 
Thesaurus+: ↑Straining and filtering devices
noun [C] UK (TRAFFIC)
► F0 a green, arrow-shaped light that is part of a set of traffic lights and tells drivers when they can turn left or right: » a traffic filter» a left/right filterSee picture: (UK) traffic filter Thesaurus+: ↑Lights, signs and markings on roads
verb [I + adv/prep] (APPEAR GRADUALLY) ↑Verb Endings for filter
► C2 to appear or happen gradually or to a limited degree: » News filtered down to us during the day.» Reports about an accident began to filter in.» Sunlight filtered through the branches.Thesaurus+: ↑Appearing and disappearingverb [T] (REMOVE) ↑Verb Endings for filter
► C2 to remove solids from liquids or gases, or to remove particular types of light, using special equipment: » The water is filtered to remove any impurities.» Devices in the two chimneys would filter (out) (= remove) radioactive dust.Thesaurus+: ↑Removing and extractingThesaurus+: ↑Separating and dividing