"A man about a horse" is a colloquial phrase used to refer to someone knowledgeable or experienced in a particular subject matter. Synonyms for this phrase include "an expert", "a specialist", "a connoisseur" or "an authority". These terms describe individuals who possess deep understanding and expertise in their field. Whether it is a subject related to sports, technology, literature, or any other discipline, these synonyms indicate someone who is well-informed and possesses a high level of competence. These individuals are often sought after for their valuable insights and opinions. So, if you come across "a man about a horse", you can be sure that you are dealing with someone with extensive knowledge in a specific area.