bas·cule /ˈbæs(ˌ)kju(ə)l/
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  Bas·cule n.  In mechanics, an apparatus on the principle of the seesaw, in which one end rises as the other falls.
  Bascule bridge, a counterpoise or balanced drawbridge, which is opened by sinking the counterpoise and thus lifting the footway into the air.
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  bascule
       n : a structure in which one end is counterbalanced by the other
           (as in a bascule bridge)