Definition of: filter

(fil′tər) noun
1. Any device or porous substance, as paper, cloth, fine clay, or charcoal, used as a strainer for clearing or purifying fluids. Compare illustration under FUNNEL.
2. Electr. A device which permits the passage of currents of certain frequencies and limits the flow of certain others, such as a band filter, which passes currents neither above nor below a given range, a high-pass filter, which selects certain high-frequency currents and a low-pass filter, which permits the flow of certain low-frequency currents; also used in power transmission.
3. Phot. A colored screen of glass, or of other translucent material, placed in front of a camera lens to control the kind and relative intensity of light waves in an exposure.
—v.t.
1. To pass (liquids) through a filter; strain.
2. To separate (solid matter) from liquid by a filter.
—v.i.
3. To pass through a filter.
4. To move slowly; leak out, as news. See synonyms under PURIFY. ♦ Homophone: philter. [<OF filtre <Med. L fēltrum. Related to FELT².]
—fil′ter·a·bil′i·ty, fil·tra·bil·i·ty (fil′trə·bil′ə·tē), fil′ter·a·ble·ness noun
—fil′ter·a·ble, fil·tra·ble (fil′·trə·bəl) adjective