A crack, fissure, or split in a surface or structure (e.g., rock, glass, wall).
地震で建物の外壁に大きな亀裂が入った。
The earthquake caused a large crack in the building's exterior wall.
古いガラスに小さな亀裂が見つかったので交換した。
A small crack was found in the old glass, so we replaced it.
岩肌の亀裂に植物の根が入り込んでいた。
Plant roots had grown into the fissures of the rock face.