What is RAC means in train reservation Tamil language?

In Tamil, "RAC" stands for ரிசர்வேஷன் அகைன்ஸ்ட் கேன்சலேஷன் (Reservation Against Cancellation).

This translates to "நிறுத்தப்பட்டதற்கு எதிரான இட ஒதுக்கீடு" in Tamil.

It means that you have a reservation on a waiting list, and if someone cancels their confirmed ticket, you will get their seat.