Nouns

(n)filterdevice that removes something from whatever passes through it
(n)filteran electrical device that alters the frequency spectrum of signals passing through it

Verbs

(v)filter, filtrate, strain, separate out, filter outremove by passing through a filter“filter out the impurities”
(v)percolate, sink in, permeate, filterpass through“Water permeates sand easily”
(v)trickle, dribble, filterrun 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”