Define muck (verb) and get synonyms. What is muck (verb)? muck (verb) meaning, pronunciation and more by It was always my job to muck out the barn. (transitive) To clean the excrement and other rubbish from the area where an animal is kept, such as a horse stable or a dog kennel. Could you muck out Toby's. Define muck out: to clean (the place where a farm animal lives): to remove animal waste and dirty hay, sawdust, etc., from — muck out in a sentence. New Words Generation Me noun July 03, Please reload the page or if you are running ad blocking disable it. To take part, or to become involved: Sign up now Log in. A lot of the people we met volunteering in New Orleans had been mucking.