Etymology: Middle English filtre, from Medieval Latin filtrum piece of felt used as a filter, of Germanic origin; akin to Old High German filz felt — more at felt
a. a porous article or mass (as of paper or sand) through which a gas or liquid is passed to separate out matter in suspension
b. an apparatus containing a filter medium
a. a device or material for suppressing or minimizing waves or oscillations of certain frequencies (as of electricity, light, or sound)
b. a transparent material (as colored glass) that absorbs light of certain wavelengths or colors selectively and is used for modifying light that reaches a sensitized photographic material — called also color filter
3. something that has the effect of a filter (as by holding back elements or modifying the appearance of something) <his work is too often viewed through the filter of race — Brent Staples> 4. software for sorting or blocking access to certain online material II. verb (filtered; filtering) Date: 1576 transitive verb 1. to subject to the action of a filter 2. to remove by means of a filter intransitive verb 1. to pass or move through or as if through a filter 2. to come or go in small units over a period of time <people began filtering in>
New Collegiate Dictionary. 2001.