To let down, as hair, or wear or let hang in loose disorder, as clothing. (Dictionary.com)
To cause untidiness and disarray in: (Dictionary.com)
(of people or their appearance) very untidy. (Cambridge Dictionary)
(of a person’s hair, clothes, or appearance) untidy; disordered. (Oxford Dictionaries)
If you describe someone’s hair, clothes, or appearance as dishevelled, you mean that it is very untidy. (Collins Dictionary)
Pretty woman with dishevelled hair.
Teenage girl with dishevelled hair.