godan verb (-ru), intransitive verb
become perfectly clear; clear up completely
Describes water, air, sky, or sound becoming completely clear and transparent, often with a sense of purity or serenity. Related to 澄む but emphasizes a thorough, complete state.
See also: 澄む
湖の水が澄み切って、底まで見える。
The lake water is perfectly clear, and you can see all the way to the bottom.
The autumn sky is crystal clear, and the stars are very beautiful.