"Work a past master" is a phrase that means to be highly skilled or experienced in a particular aspect of work or activity. Some synonyms for this phrase include being a virtuoso, having a mastery, being an expert, being a pro, being a specialist, being a whiz, or being a seasoned veteran. These terms all indicate a level of proficiency and expertise that comes with years of practice and dedication. Whether it is in sports, music, or the workplace, someone who has worked as a past master commands respect and admiration, and these synonyms all reflect that level of accomplishment.