Definition of "redundant"

It is allowed, that Senates and great Councils are often troubled with redundant, ebullient, and other peccant Humours, with many Diſeaſes of the Head and more of the Heart; [...]

1726 October 28, [Jonathan Swift], “A Further Account of the Academy. […]”, in Travels into Several Remote Nations of the World. […] [Gulliver’s Travels], volume II, London: […] Benj[amin] Motte, […], part III (A Voyage to Laputa, Balnibarbi, Glubbdubdribb, Luggnagg, and Japan), page 82

In the living state, the body is observed to receive aliment; to assimilate a part; to evacuate what is redundant or useless; [...]

1822, John Barclay, chapter I, in An Inquiry Into the Opinions, Ancient and Modern, Concerning Life and Organization‎, Edinburgh, London: Bell & Bradfute; Waugh & Innes; G. & W. B. Whittaker, section I, page 1

A key driver has been the approval of a new housing and employment development called Fawley Waterside, with 1,500 homes planned on the site of a redundant power station on the edge of Southampton Water.

2020 December 16, “Network News: "Robust case" for Fawley branch reopening”, in Rail, page 14

Two entrants shared this award for their work on two quite different stations, but with the same purpose of bringing a redundant station building back into use for the benefit of the community, with the added result of conserving an historic building.

2021 December 15, Robin Leleux, “Awards honour the best restoration projects: The Network Rail Community Award: Saltash and Stow”, in RAIL, number 946, page 58

The two lines are mainly used for redundant and therefore fault-tolerant message transmission, but they can also transmit different messages.

2013, Tom Denton, Automobile Electrical and Electronic Systems, page 142