What does "anabranch" mean?

Anabranch: A branch of a river that reënters, or anastomoses with, the main stream; also, less properly, a branch which loses itself in sandy soil. [Australia] Such branches of a river as after separation reunite, I would term anastomosing branches; or, if a word might be coined, anabranches, and the islands they form branch islands. Col. Jackson.