The phrase "boring master" could refer to someone who is dull or uninteresting as a teacher or instructor. Some synonyms for this term might include tedious, unengaging, or uninspired. Other options could include unstimulating, uninspiring, or lackluster. These terms suggest that the individual may not have the ability to captivate their students with their teaching style or subject matter. Additionally, the phrase "boring master" could imply that the individual is unapproachable or unexciting as a mentor or guide. Synonyms for this could include drab, dreary, or unremarkable. Regardless of the specific wording chosen, it is clear that a "boring master" is someone who fails to engage and inspire those they are meant to lead.