The phrase "hard master" denotes someone who is strict or demanding in their authority. Synonyms for this phrase include "strict teacher", "rigorous boss", "tough supervisor", "stern manager", "harsh taskmaster", and "stringent director". These synonyms denote individuals who expect high standards of work and behavior from those under their command. They may come across as intimidating or fearsome, but they are also often respected for their ability to push their charges to their full potential. While working under a hard master may be challenging, it can also lead to personal growth and development under their guidance.