steep bank; cliff
Refers to a steep, often eroded, natural slope or cliff, typically along a river or coast.
川沿いの切り岸が崩れそうで危ない。
The steep bank along the river looks like it might collapse and is dangerous.
その海岸には高い切り岸が続いている。
Along that coast, there is a stretch of high cliffs.
Compound of 切り (kiri, 'cutting') + 岸 (kishi, 'bank/shore'), referring to a bank that appears cut or steep. The exact historical derivation is uncertain.