I. ˈfiltə(r) noun
( -s )
Usage: often attributive
Etymology: Middle English filtre, from Medieval Latin filtrum felt, piece of felt used for straining liquids, of Germanic origin; akin to Old Saxon filt felt — more at felt
1. : a porous article or mass (as of cloth, paper, or sand) that serves as a medium for separating from a liquid or gas passed through it matter held in suspension or dissolved impurities or coloring matter: as
a. : a circular piece of filter paper folded twice or fluted to fit a conical funnel or used flat (as in a Büchner funnel) especially for laboratory filtrations
b. also filter candle : a candle-shaped hollow cylinder closed at one end and made of diatomite or unglazed porcelain with minute pores that prevent the passage of cells or bacteria and other microscopic organisms but not of ultramicroscopic bodies (as the filterable viruses)
2.
a. : an apparatus (as a tube or tank) containing a filter medium and operating by gravity, pressure, or vacuum
b. : trickling filter
3. : a device or material for suppressing or minimizing waves or oscillations of certain frequencies passing through it without greatly altering the intensity of others:
a. : a combination of capacitors and inductors in an electric circuit that transmits only frequencies within a selected band — called also band-pass filter ; see high-pass filter , low-pass filter
b. : a transparent material (as glass or gelatin) that usually transmits radiant energy of some wavelengths more freely than others, interference and polarization effects being used in some types : color filter
c. : a tube or a combination of tubes, branch tubes, orifices, and resonant cavities in a sound channel that limits the frequency range of sounds passing through it — called also acoustic filter
II. verb
( filtered ; filtered ; filtering -t(ə)riŋ ; filters )
Etymology: Medieval Latin filtrare, from filtrum
transitive verb
1. : to subject to the action of a filter : pass (a liquid or gas) through a filter for the purpose of purifying or separating or both : strain ; also : to act as a filter toward
2. : to remove from a fluid by means of a filter — usually used with off or out
filter off impurities
intransitive verb
1.
a. : to pass through or as if through a filter : percolate
b. of light : to pass through something that partially obstructs
daylight filtering through thick clouds — Francis Stuart
sunlight filtering through the shutters — T.B.Costain
2.
a. : infiltrate 2
filter through the front lines
b. : to enter or cross over in small units over a period of time
races which filtered into Europe toward the end of the old stone age — Emma Hawkridge