Possible Definitions:
1. Filter (n.) Any porous substance, as cloth, paper, sand, or charcoal, through which water or other liquid may passed to cleanse it from the solid or impure matter held in suspension; a chamber or device containing such substance; a strainer; also, a similar device for purifying air.
2. Filter (n.) To purify or defecate, as water or other liquid, by causing it to pass through a filter.
3. Filter (v. i.) To pass through a filter; to percolate.
4. Filter (n.) Same as Philter.
