filter

fil|ter¹ [ˈfıltə US -ər] n

[Date: 1300-1400; : Old French; Origin: filtre 'piece of felt (= thick material) used as a filter', from Medieval Latin filtrum]

1.) something that you pass water, air etc through in order to remove unwanted substances and make it clean or suitable to use

water/air/oil etc filter

▪ a pond filter

▪ coffee filter papers

▪ filter cigarettes (=with a filter at the end)

2.) a piece of equipment or computer program that only allows certain sounds, images, signals, types of information etc to pass through it

▪ a UVA light filter

▪ The firm uses electronic filters to prevent workers from accessing the Internet.

3.) BrE a traffic light that shows car drivers when they can turn right or left

filter ²

filter² v

1.) [T]

to remove unwanted substances from water, air etc by passing it through a special substance or piece of equipment

▪ The water in the tank is constantly filtered.

▪ The ozone layer filters harmful UV rays from the sun.

2.) [I always + adverb/preposition]

if people filter somewhere, they move gradually to that place

▪ Chattering noisily, the crowd began to filter into the auditorium.

3.) [I always + adverb/preposition]

if news, information etc filters somewhere, people gradually hear about it from each other

▪ The news gradually filtered through from Bombay last night.

4.) [I always + adverb/preposition]

if light or sound filters into a place, it can be seen or heard only slightly

▪ Moonlight filtered in through the frosted window.

▪ The familiar notes of Beethoven's 'Für Elise' filtered from the bar.

5.) [I and T] BrE

if traffic filters, or if a system filters it, cars can turn left or right while other vehicles going straight ahead must wait

filter out [filter sth<=>out] phr v

1.) to remove something, using a filter

▪ The pump filters out mud.

2.) to remove words, information etc that you do not need or want

▪ Net users can filter out unwanted emails with software.