noun
wave-dissipating concrete block; tetrapod
A concrete block placed along coastlines to absorb wave energy and prevent erosion. Often called a tetrapod, though that is a specific brand name.
See also: 消波ブロック
海岸に波消しブロックが並んでいる。
Wave-dissipating blocks are lined up along the shore.
Wave-dissipating blocks are also called 消波ブロック.