n.
   - a porous device for removing impurities or solid particles from a liquid or gas passed through it. ▸a screen, plate, or layer which absorbs some of the light passing through it. ▸a device for suppressing electrical or sound waves of frequencies not required. 
- Brit. an arrangement whereby vehicles may turn left (or right) while other traffic waiting to go straight ahead or turn right (or left) is stopped by a red light.
- Computing  a piece of software that processes data before passing it to another application, for example to remove unwanted material.
v.
  - pass through a filter.
- 
(often filter in/out/through)
 move or pass into something slowly or gradually. ▸(of information) gradually become known. 
Derivative
  
    
      - filterable 
(also filtrable)
 adj.
 
  Etymology
  ME (denoting a piece of felt): from Fr. filtre, from med. L. filtrum ‘felt used as a filter’, of W. Gmc origin and rel. to felt1.