A man of his word is someone who keeps their promises and follows through on their commitments. Synonyms for this phrase could include honorable, trustworthy, reliable, upright, faithful, and dependable. These synonyms all suggest a person with strong moral character who can be counted on to do what they say they will do. Other potential synonyms might include sincere, honest, principled, and ethical. Regardless of the specific term used to describe such a person, the implication is that they are someone who can be trusted and relied upon, both in personal relationships and in professional contexts.