also: みずぶち
noun
water spot; water stain
Refers to a dried water mark left on a surface, such as on dishes, glass, or metal after washing.
グラスに水斑が残らないように、すぐに拭いてください。
Wipe the glasses right away so water spots don't remain.
洗った皿に白い水斑がついている。
There are white water spots on the washed dishes.
Compound of 水 (water) and 斑 (spot, speckle). The reading すいはん is the on'yomi, while みずぶち uses the kun'yomi for 水 and an irregular reading for 斑.