1) Crinkle 2) Fold 3) Ridge 4) Roughness 1) Fold 2) Furrow 3) Ridge 
• (n.) The act corrugating; contraction into wrinkles or alternate ridges and grooves.
Cor`ru·ga'tion noun [ Confer F. corrugation .] The act corrugating; contraction into wrinkles or alternate ridges and grooves. 
[n] - a ridge on a corrugated surface 2. [n] - the act of shaping into parallel ridges and grooves
corrugation Formed or shaped into wrinkles, folds, or into alternating ridges and grooves.
noun the act of shaping into parallel ridges and grooves
the act or state of corrugating or of being corrugated. · a wrinkle; fold; furrow; ridge.