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.
Main Entry: filterable virus Variant: alsofiltrable virus Function: noun : any of the infectious agents that pass through a filter especially ofdiatomite or unglazed porcelain with the filtrate and remain virulent and that include the viruses as presently understood and various other groups (as the mycoplasmas and rickettsias) which were orig.considered viruses before their cellular nature was established
