There are a number of different ways to express the idea of the "final word," which refers to the ultimate decision or conclusion in a given matter. Synonyms for this phrase might include "ultimate say," "conclusive verdict," "ultimate decision," "decisive conclusion," "final decree," or "definitive ruling." All of these variations convey a sense of authority, finality, and closure, indicating that a decision has been made and that there is no further debate or discussion to be had. Different synonyms may be more appropriate depending on the context and the tone of the conversation, but they all communicate the idea of a definitive ending point.