filter

ot noun

1. Any item, mechanism, device or procedure that acts to separate or isolate. He runs an email filter to catch the junk mail.
2. Self-restraint in speech. He's got no filter, and he's always offending people as a result.
3. A non-empty upper set (of a partially ordered set) which is closed under binary infima (a.k.a. meets). If (1) the universal set (here, the set of natural numbers) were called a "large" set, (2) the superset of any "large" set were also a "large" set, and (3) the intersection of a pair of "large" sets were also a "large" set, then the set of all "large" sets would form a filter.
4. A device which separates a suspended, dissolved, or particulate matter from a fluid, solution, or other substance; any device that separates one substance from another.

fe’l verb

1. To sort, sift, or isolate. This strainer should filter out the large particles.
2. To diffuse; to cause to be less concentrated or focused. The leaves of the trees filtered the light.
3. To pass through a filter or to act as though passing through a filter. The water filtered through the rock and soil.
4. To move slowly or gradually; to come or go a few at a time. The crowd filtered into the theater.