From the plane, we had a breathtaking view of the rugged coastline below.

coastline 是由 coast（海岸）和 line（线）组成的复合名词，字面意思是"海岸线"，指陆地与海洋交界处的轮廓线。rugged coastline 特指那些崎岖不平、多岩石的海岸线。