If you describe a person as untidy, you mean that they do not care about whether things are neat and well arranged, for example in their house. I'm untidy in most ways. tidy
If you describe something as untidy, you mean that it is not neat or well arranged. The place quickly became untidy. a thin man with untidy hair Clothes were thrown in the luggage in an untidy heap. tidy + untidily un·ti·di·ly Her long hair tumbles untidily around her shoulders. the desk piled untidily with books and half-finished homework. + untidiness un·ti·di·ness The dust and untidiness in her room no longer bothered her. tidiness
not neat and tidy; "careless and untidy in her personal habits"; "an untidy living room"; "untidy and casual about money"