| an arm of the Gulf of Mexico, extending from Lake Borgne, SE Louisiana, to Mobile Bay, SW Alabama: part of the Intracoastal Waterway. ab. 100 mi. (160 km) long. |
| Mississippi Sound An arm of the Gulf of Mexico bordering on southeast Louisiana, southern Mississippi, southwest Alabama, and a chain of small offshore islands. It is part of the Intracoastal Waterway. |