n.a substance (such as sodium chloride) that lessens the hardness of water by replacing calcium and magnesium ions with sodium ions and so gives the water more efficient sudsing power
同义词：water softener
英汉双解大词典
water softener
1.
N（名词）
any substance that lessens the hardness of water, usually by precipitating or absorbing calcium and magnesium ions 软水剂