Wave cloud

That wave cloud pattern formed over the Île Amsterdam, in the lower left corner at the tip of the triangular formation, in the far southern Indian Ocean.

A wave cloud is a cloud form created by atmospheric internal waves.

Wave cloud pattern in Tadrart region.
Unusual wave clouds over the Aral Sea, seen from NASA's Water satellite on March 12, 2009.
Wave cloud pattern in Germany on August 25, 2020.
Wave clouds in various directions.