The phrase "muck around" generally means wasting time or doing something without any specific purpose. There are several synonyms that can be used in place of "muck around" in order to make your speech or writing more interesting and expressive. Some of the alternatives include "idle away," "lollygag," "fritter away," "dillydally," "waste time," "faff about," and "tinker aimlessly." Each of these phrases can be used in slightly different contexts depending on the situation. However, they all carry a sense of wasting time or doing unproductive activities, which is the essence of "muck around." So next time, you can replace "muck around" with these synonyms to add some variety to your language.