1 sieve, colander, riddle, screen, strainer, gauze, cloth, cheesecloth, membrane:
To allow the liquid to pass through, a clean filter must be used.
2 Sometimes, filter out. strain, screen, sift, winnow, clarify, refine, purify, clean; separate, weed out, exclude, eliminate:
Some people filter tap water to improve its taste. This company would be improved if we could filter out the undesirable elements.
3 leach, percolate, drip, seep, dribble, trickle, drain, run or pass through, ooze:
The rainwater is filtered through fine sand to purify it.