su·per·in·cum·bent /-ɪnˈkʌmbənt/
  (a.)橫在上面的,在上面的,自上面的
  Su·per·in·cum·bent a.  Lying or resting on something else.
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  superincumbent
       adj : lying or resting on and exerting pressure on something else;
             "superincumbent layers of dead plants cut off the air
             and arrested decomposition"