Noun

• S: (n) filter (device that removes something from whatever passes through it)
• S: (n) filter (an electrical device that alters the frequency spectrum of signals passing through it)

Verb

• S: (v) filter, filtrate, strain, separate out, filter out (remove by passing through a filter) "filter out the impurities"
• S: (v) percolate, sink in, permeate, filter (pass through) "Water permeates sand easily"
• S: (v) trickle, dribble, filter (run or flow slowly, as in drops or in an unsteady stream) "water trickled onto the lawn from the broken hose"; "reports began to dribble in"