A stakeholder holding power, legitimacy and urgency at once, whose claim takes priority over every other claim on the work.
A definitive stakeholder can affect the outcome, holds a claim that is generally accepted as proper, and is pressing that claim now. Because all three attributes are present together, the claim is the one that gets answered first, ahead of stakeholders who may be individually more powerful but are missing one of the three. Most definitive stakeholders arrive in the class rather than starting there, usually by acquiring the attribute they lacked: a dependent stakeholder who finds a powerful advocate, or a dominant one whose settled claim suddenly becomes time critical.
See also
A stakeholder classification that sorts claims by three attributes, power, legitimacy and urgency, producing seven classes plus the nonstakeholder.
Identifying who holds a claim on a piece of work and classifying those claims, so that attention is allocated deliberately rather than by whoever shouts loudest.
Where this comes up
One row per stakeholder, one column per engagement level, and two marks per row. The distance between the two marks is the only thing on the grid you can actually act on.
Three attributes, seven classes, one question: whose claim gets attention first. Hold all three and you are a definitive stakeholder, and definitive stakeholders do not wait.
A reward is set in advance and conditional. Recognition is retrospective, unexpected and free. Most project managers control the second and none of the first, which decides where the effort goes.