Countermand is a verb that means to revoke an order. 

Our word of the day combines the Latin prefix C-O-N-T-R-A which means ‘against,’ and the Latin word mandare (man DARE ay) which means ‘to order.’ Countermand dates back to the late Middle English period. Here’s an example:

I had previously ordered all employees to be fired if they showed up late, but when it became clear that such an edict would result in the complete eradication of our workplace, I decided to countermand my decree. I guess you could say I had a history of reversing previous orders once I realized they didn’t make sense.