A river of the south-central United States rising in two branches in the Texas Panhandle and flowing about 1,638 km (1,018 mi) eastward along the Texas-Oklahoma border and into Arkansas, where it changes direction and flows southward into Louisiana and then southeast to the Mississippi River.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.