"Hair is a mess" 或 "Hair is disheveled" 都可以用来形容发型乱了。

这两个表达都可以用来描述人的头发看起来凌乱、不整洁、杂乱无章的样子。

一些例句如下:

She woke up with her hair a mess. (她醒来时发型乱了。)
His hair was disheveled after the wind blew through it. (风吹过后,他的头发乱了。)
I need to fix my hair. It's a mess. (我得把头发整理一下。太乱了。)

注意,"a mess" 和 "disheveled" 都是形容词,都可以用来修饰名词 "hair"。