The Collaborative International Dictionary of English v.0.48:

Corrugate \Cor"ru*gate\ (-g?t), v. t. [imp. & p. p. Corrugated
   (-g?`t?d); p. pr. & vb. n. Corrugating (-g?`t?ng).]
   To form or shape into wrinkles or folds, or alternate ridges
   and grooves, as by drawing, contraction, pressure, bending,
   or otherwise; to wrinkle; to purse up; as, to corrugate
   plates of iron; to corrugate the forehead.
   [1913 Webster]

   Corrugated iron, sheet iron bent into a series of alternate
      ridges and grooves in parallel lines, giving it greater
      stiffness.

   Corrugated paper, a thick, coarse paper corrugated in order
      to give it elasticity. It is used as a wrapping material
      for fragile articles, as bottles.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

corrugated \corrugated\ adj.
   shaped into parallel folds alternately grooved and ridged;
   as, the surface of the ocean was rippled and corrugated.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

corrugated
    adj 1: shaped into alternating parallel grooves and ridges; "the
           surface of the ocean was rippled and corrugated"