back·wa·ter /-ˌwɔtɚ/
  死水,滯水,停滯,回水
  Back·wa·ter n.
  1. 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.
  2. An accumulation of water overflowing the low lands, caused by an obstruction.
  3. Water thrown back by the turning of a waterwheel, or by the paddle wheels of a steamer.
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  backwater
       n 1: 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"
       2: any backward region that is isolated from the world and
          resists progress