ReKey is a locksmith term, and it means to replace the key used in a lock. The word “rekey” is often shortened to just “key.” Rekeys are often done when someone has lost their keys or needs extra keys for security purposes. A locksmith will generally take the old key out of an existing lock, cut off any metal shanks that have been protruding from the sides, put in a new key with different profile shapes, and return everything back into place so you can use your lock again.