Definitions for "Window period"
See seroconversion.
the time span between the date of an initial tuberculin skin test with a negative reaction and the date of the follow-up tuberculin skin test that should take place 10 to 12 weeks after exposure; after the window period has ended, a repeat skin test should be administered to each contact who had an initial negative reaction
a time when HIV is not detected in a blood sample, but can be passed on through contact with the blood