- diagnostic [dī΄əg näs′tik]adj.[ML diagnosticus < Gr diagnōstikos]1. of or constituting a diagnosis2. of value for a diagnosis; specif., characteristic3. Comput. of or having to do with the use of computer diagnosticsn.1. [usually pl., with sing. v.] the art, science, or method of diagnosis, esp. medical diagnosis2. a distinguishing sign or symptom; characteristic3. Comput. a routine for testing a piece of hardware or for locating an error in a programdiagnosticallyadv.
English World dictionary. V. Neufeldt. 2014.