| 1. | the branch of governmental service that conducts secret investigations, esp. investigations into the military strength of other nations. |
| 2. | (initial capital letters ) the branch of the U.S. Department of the Treasury charged chiefly with the discovery and apprehension of counterfeiters and with providing protection for the president and the president's immediate family. |
| 3. | secret work for a government, esp. espionage. |
A division of the United States Department of the Treasury, responsible for apprehending counterfeiters; investigating a variety of federal crimes; and protecting presidents and their families, presidential candidates, and foreign dignitaries visiting the United States.