Definition of Missouri

• a midwestern state in central United States; a border state during the American Civil War, Missouri was admitted to the Confederacy without actually seceding from the Union
• the longest river in the United States; arises in Montana and flows southeastward to become a tributary of the Mississippi at Saint Louis; "The Missouri and Mississippi Rivers together form the third longest river in the world"
• a member of the Siouan people formerly inhabiting the valley of the Missouri river in Missouri