proxy

Definitions:

The person who is substituted to act for another; the agency of a substitute; the writing by which one person is authorised to vote for another.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
To vote or act by the agency of another.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (verb) (v.) (verb)
The agency of another who acts as a substitute; one deputed to act for another; a writing granting this power; substitute.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)
An agent; substitute; act empowering an agent.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (noun) (n.) (noun)
A person with authority to act for another; the document by which one person is authorized to act or vote for another.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)
The agency of one who acts for another: one who acts for another, or the writing by which he is deputed.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (noun) (n.) (noun)

Usage examples:

Here am I, who have suffered pretty nearly as much as St. Paul, have forgiven all my enemies all round, and shaken hands with the Marquis by proxy while Puddleham has been man enough to maintain the dignity of his indignation.
- The Vicar of Bullhampton by Anthony Trollope
This circumstance drew together an amazing concourse of people to witness the ceremony, which, on the bride's part, was literally performed by proxy
- Anecdotes & Incidents of the Deaf and Dumb by W. R. Roe
Perhaps we may say she was married by proxy when her family sent her away with blessings and good wishes.
- A Letter of Credit by Susan Warner