A porous material through which a liquid or gas is passed in order to separate the fluid from suspended particulate matter, A colored glass or other transparent material used to select the wavelengths of light allowed to reach a photosensitive material, A device for arresting and separating any matter mechanically suspended in a liquid, intransitive verb_ To pass through a filter; to percolate, transitive verb_ To purify or defecate, as water or other liquid, by causing it to pass through a filter, a porous unsized paper, for filtering, verb_ remove by passing through a filter, pass through