corrugations is a form of:

Corrugation



noun
1.
(វេជ្ជសាស្ត្រ) ភាពជ្រួញ
2.
ភាពរួញ, ភាពជ្រួញៗ
ENGLISH MEANING
noun
1.
The act corrugating; contraction into wrinkles or alternate ridges and grooves.