To Crumble, To Collapse
intransitive verb, ichidan verb
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means crumble and the verb vocab version means to crumble, like, something is crumbling or collapsing.
くずれる
The reading comes from 崩す, so if you know that you know this reading as well!
ああっ！またお化粧が崩れてきちゃった。
Oh no! My make-up is coming off again.