When you revoke something, you officially cancel it, like when you revoke your sister's "coolest sibling" award because she shows your friends funny pictures of you from when you were little.
The verb revoke comes from the Latin word revocare, meaning "to call back or rescind." Licenses, wills, and privileges are three things that can be revoked. The verb also has a meaning specific to card- playing. If the rules state that you have to follow suit, but you accidentally play trump instead, you have revoked or reneged. If other players notice your mistake, you have to take the card back.