Quiz: Remember the definition of mal de mer?
early 15c., from Old French filtre and directly from Medieval Latin filtrum "felt," which was used to strain impurities from liquid, from West Germanic *filtiz (see felt (n.)). Of cigarettes, from 1908.
1570s, from Medieval Latin filtrare, from filtrum (see filter (n.)). The figurative sense is from 1830. Related: Filtered; filtering.
filter fil·ter (fĭl'tər)
A porous material through which a liquid or gas is passed in order to separate the fluid from suspended particulate matter.
A device containing such a substance.
Any of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or radiations of certain frequencies while passing others.
A translucent screen, used in both diagnostic and therapeutic radiology, that permits the passage of rays having desirable levels of energy.
A device used in spectrophotometric analysis to isolate a segment of the spectrum.
To pass a liquid or gas through a filter.
To remove by passing through a filter.
To pass through or as if through a filter.
1. (Originally Unix, now also MS-DOS) A program that processes an input data stream into an output data stream in some well-defined way, and does no I/O to anywhere else except possibly on error conditions; one designed to be used as a stage in a pipeline (see plumbing). Compare sponge.
2. (functional programming) A higher-order function which takes a predicate and a list and returns those elements of the list for which the predicate is true. In Haskell:
filter p  =  filter p (x:xs) = if p x then x : rest else rest where rest = filter p xs
See also filter promotion.