Short for "unknown subject," often used in criminal investigations to refer to an unidentified perpetrator.

अज्ञात विषय

English Usage: The detective was seeking leads on the unsub behind the recent spree of burglaries.

Hindi Usage: जासूस हाल की चोरी की लहर के पीछे के unsub पर सुराग की तलाश कर रहा था।