Dictionary.com
definitions

Potomac

[puh-toh-muh k]

noun

a river flowing SE from the Allegheny Mountains in West Virginia, along the boundary between Maryland and Virginia to the Chesapeake Bay. 287 miles (460 km) long.
a city in central Maryland, near Washington, D.C.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for potomac river

Potomac

noun

a river in the E central US, rising in the Appalachian Mountains of West Virginia: flows northeast, then generally southeast to Chesapeake Bay. Length (from the confluence of headstreams): 462 km (287 miles)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for potomac river

Potomac

river in eastern U.S., from Algonquian Patowmeck, originally the name of a native village in Virginia, perhaps literally "something brought."

Online Etymology Dictionary, © 2010 Douglas Harper
potomac river in Culture

Potomac River

[(puh-toh-muhk)]

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.”
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.