filter

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.

Electronics or software that separates unwanted signals (for example noise) from wanted signals or that attenuates selected frequencies.

Any item, mechanism, device or procedure that acts to separate or isolate.

“He runs an email filter to catch the junk mail.”

Self-restraint in speech.

“He's got no filter, and he's always offending people as a result.”

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.”

To sort, sift, or isolate.

“This strainer should filter out the large particles.”

To diffuse; to cause to be less concentrated or focused.

“The leaves of the trees filtered the light.”

To pass through a filter or to act as though passing through a filter.

“The water filtered through the rock and soil.”

To move slowly or gradually; to come or go a few at a time.

“The crowd filtered into the theater.”

To ride a motorcycle between lanes on a road

“I can skip past all the traffic on my bike by filtering.”