: any of the infectious agents that remain virulent after a fluid containing them passes through a filter of diatomite or unglazed porcelain and that include the viruses as presently understood and various other groups (as the mycoplasmas and rickettsias) which were originally considered viruses before their cellular nature was established — see virus 2b
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a virus particle small enough to pass through a filter of diatomaceous earth or porcelain, which will not pass bacteria: chiefly historical or an informal indicator of size, as synthetic membrane filters now permit passage of the smallest virus.
[1910-15]
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filˈter-passer or filterable virus noun
Terms used formerly for a virus in the sense of submicroscopic disease agent
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Main Entry: ↑filter
Useful english dictionary. 2012.