1. to have the final word in an argument or to have the authority to make the ultimate decision
have the final say on the matter
When you have 'the final say', it means you're the last person to speak or to have the last word in an argument or dispute. It can also mean the person or authority who has the power to make a final or ultimate decision on a matter. This is an idiomatic expression that can be used in social and professional contexts.