the agency, function, or power of a person authorized to act as the deputy or substitute for another.

the person so authorized; substitute; agent.

a written authorization empowering another person to vote or act for the signer, as at a meeting of stockholders.

an ally or confederate who can be relied upon to speak or act in one's behalf.

noun

alternate , ambassador , assignee , attorney , backup , broker , delegate , deputy , emissary , envoy , executor , intermediary , lawyer , mediary , negotiator , representative , stand-in , substitute , surrogate , agent , authority , proctor , procurator , vicar , vote