An evidentiary rule or common law doctrine under which a party's disclosure of privileged or work product-protected communications or information removes the attorney-client privilege or work product protection for related, but undisclosed, communications or information. This allows other parties to seek discovery of otherwise protected communications or information concerning the same subject matter.

For more information on the scope of an attorney-client privilege or work product protection waiver, see Practice Notes, Attorney-Client Privilege: Waiver (Federal) and Work Product Protection: Waiver (Federal).