[puh-toh-muh
k] 
| 1. | a river flowing SE from the Allegheny Mountains in West Virginia, along the boundary between Maryland and Virginia to the Chesapeake Bay. 287 mi. (460 km) long. |
| 2. | a city in central Maryland, near Washington, D.C. 40,402. |
| Po·to·mac River (pə-tō'mək) A river of the east-central United States rising in northeast West Virginia and flowing about 459 km (285 mi) along the Virginia-Maryland border to Chesapeake Bay. It is navigable for large ships to Washington, D.C. |
A river that divides Washington, D.C., from Virginia.
Note: Sometimes used to refer loosely to Washington, D.C.: “Along the Potomac today, Congress met to vote on the budget.”