a body of water that was created by a flood or tide or by being held or forced back by a dam
The bayous and backwaters are breeding grounds for mosquitos.
source: WordNet 3.0
a place or condition in which no development or progress is occurring
The country is an economic backwater.
source: WordNet 3.0
Water turned back in its course by an obstruction, an opposing current, or the flow of the tide, as in a sewer or river channel, or across a river bar.