A patent application may be expressly abandoned by filing a written declaration of abandonment identifying the application in the United States Patent and Trademark Office. Express abandonment becomes effective when an appropriate official of the Office takes action thereon. Express abandonment of the application may not be recognized by the USPTO before the date of issue or publication unless it is actually received by appropriate officials in time to act. Abandonment may be either of the invention or of an application. An abandoned application, in accordance with 37 CFR 1.135 and 1.138, is one which is removed from the USPTO docket of pending applications.
Source: U.S. Patent and Trademark Office.