Wabash, waw'bash, a river rising in the western part of Ohio, flowing northwestward, westward and then southward. It crosses Indiana, in the latter part of its course forms a part of the boundary between Indiana and Illinois, and enters the Ohio about 30 miles below Evansville, Ind. Its length is 550 miles, and it is navigable during high water as far as Lafayette, Ind., and in ordinary stages to Covington. Its chief tributary is the White River. Some of the principal towns on its banks are Wabash, Peru, Logansport, Lafayette, Covington, Terre Haute and Vincennes.