(n)tuberculin (a derivative of tubercle bacillus) is injected intradermally; a red area appearing 1-3 days later signifies an exposure (past or present) to tubercle bacilli and the need for further testing
The Collaborative International Dictionary of English (GCIDE) v.0.53Collaborative International Dictionary (GCIDE)
prop. n. (Med.) A skin test for hypersensitivity to tuberculin. It determines whether there is or has been any infection with tubercle bacilli. [ WordNet 1.5 ]