cor·ru·ga·tion /ˌkɔrəˈgeʃən, ˌkɑr-/
  起皺,成皺,皺狀
  Cor·ru·ga·tion n.  The act corrugating; contraction into wrinkles or alternate ridges and grooves.
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  corrugation
       n 1: a ridge on a corrugated surface
       2: the act of shaping into parallel ridges and grooves