corrugation

US /ˌkɔːr.əˈɡeɪ.ʃən/
UK /ˌkɔːr.əˈɡeɪ.ʃən/
1.

beralun

a line or fold on the surface of something:

:
•
The dirt road is full of corrugations which make it unsuitable for RVs.
:
corrugated