The quantity of a cytopathogenic agent, such as a virus, that will produce a cytopathic effect in 50% of the cultures inoculated. ... (05 Mar 2000) ... 
(TCID50, TCD50) Type: Term Definitions: 1. the quantity of a cytopathogenic agent, such as a virus, that will produce a cytopathic effect in 50% of the cultures inoculated.