To cause something to become disheveled or untidy, especially one's hair. A noun or pronoun can be used between "muss" and "up." I just spent an hour getting my hair exactly how I want it, so don't go mussing it up like that!Please don't muss up your hair before you get your pictures taken for school.
All content on this website, including dictionary, thesaurus, literature, geography, and other reference data is for informational purposes only. This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional.