Taking action that is futile or no longer necessary because the problem has already occurred or the opportunity has already passed.

देर से समाधान निकालना, जब समस्या पहले से ही हो चुकी हो।

English Usage: Trying to implement safety measures after an accident has happened is like closing the stable door after the horse has bolted.

Hindi Usage: दुर्घटना हो जाने के बाद सुरक्षा उपाय लागू करना बेकार की कोशिश करने जैसा है।