cor·ru·gate 
(kôrə-gāt′, kŏr-)
(kôrə-gāt′, kŏr-)v. cor·ru·gat·ed, cor·ru·gat·ing, cor·ru·gates
v.tr.
To shape into folds or parallel and alternating ridges and grooves.
v.intr.
To become shaped into such folds or ridges and grooves: "Now the immense ocean ... sensed the change. Its surface rippled and corrugated where sweeping cloud shadows touched it" (John Updike).
[Latin corrūgāre, corrūgāt-, to wrinkle up : com-, com- + rūgāre, to wrinkle (from rūga, wrinkle).]
corru·gate′, corru·gat′ed (-gā′tĭd) adj.