godan verb (-su), transitive verb
wear casually; dress down formal clothes
Used for wearing formal clothing such as a suit or kimono in a relaxed, untidy, or intentionally casual way, often by loosening or not following proper form.
彼はスーツを着崩して、ネクタイを外していた。
He wore his suit casually, with his tie off.
着物を着崩すと、だらしなく見
If you wear a kimono sloppily, it looks untidy.