Diagnostic/ˌdaɪəɡˈnɑːstɪk/ Definition 1 of 4Pro Tip 1/3Medical Context Used mainly in healthcare to refer to identifying diseases. Her diagnostic procedure confirmed the type of infection. Pro Tip 2/3Precise Identification Implies a precise detection, not a general check-up. The diagnostic tool pinpointed the exact location of the fracture. Pro Tip 3/3Not Always Illness Can refer to any condition, not just illnesses, like pregnancy. A pregnancy test is a diagnostic test too.